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04 Jan 2007

Why Doesn't Bill Polian's S--t Work in the Playoffs?

"My shit doesn't work in the playoffs."

- Billy Beane, as quoted by Michael Lewis in Moneyball

Let's just get that quote out of the way -- you and I both know that it's an essential part of any sabermetric discussion of playoff performance.

Beane's Axiom doesn't just apply, of course, to the Oakland Athletics, Jeremy Giambi, the playoffs, or even baseball; it's a simple way of pointing out that the variance over a seven-game sample size is impossible to control for in the same way that you can over the course of a 162-game season. Beane's statement is as hopeless as it is simple. It's also incorrect.

My colleagues at Baseball Prospectus analyzed Beane's statement in last year's Baseball Between The Numbers, in a chapter titled, naturally, "Why Doesn't Billy Beane's Shit Work In The Playoffs?" You can read an edited version of the chapter on ESPN here.

What Nate Silver and Dayn Perry found were that the traditional ideas of what led to playoff success, namely pitching and defense, were correct. The three variables that were the most likely predictors of postseason performance were the performance of the team's closer, the strikeout rates of their pitchers, and the performance of the team's defense. Offensive performance showed no such significance in predicting postseason success.

It's with this work in mind that I decided to do the same research on predicting performance within the NFL playoffs here at Football Outsiders. While the work done on baseball looked at data from 1972 on, we at FO currently have DVOA figures going back to 1997, leaving nine years of playoff performances to be analyzed. While the traditional data is available for seasons before 1997, our advanced DVOA metric does a better job of adjusting for context and proves a truer measure of teams' abilities and performances.

(For anyone new to Football Outsiders, our DVOA stats break down every single play, measuring success towards both a touchdown and a first down, and compare to a league baseline based on situation and opponent. More is explained here. "Weighted" DVOA is a version of DVOA that gives more weight to late-season games over early-season games.)

For example, there's been a lot of talk this year about how the Colts have the worst rush defense, perhaps in football history, with their high yards per carry allowed given as the reasoning behind such a claim. That ignores the fact that the Colts are often ahead in games and are putting their defense in situations where the average team gives up more running yards and yards per carry than they would if they, say, were the Raiders and losing all the time. DVOA measures a team's performance versus the average performance of a team in the same situation, as opposed to all situations. Of course, the Colts still can't stop the run -- they rank 31st in run defense DVOA -- but they're not even the worst team in the playoffs. That honor goes to the Jets, who profile as slightly worse than Indianapolis.

To measure the success of each team within the playoffs, I created a quick and dirty metric similar to Nate and Dayn's Playoff Score Points. The idea is to reward teams that win the Super Bowl over all else, but also to note the performance of teams who perform well without doing so. In that vein, each team was given:

  • 2 points for winning a playoff game at home
  • 3 points for winning a playoff game on the road
  • 5 points for winning the Super Bowl (at a neutral venue)

I am amenable to the idea that this system might punish teams that get a first round bye slightly, but at the same time, those teams simply didn't need to perform as well once they made it to the playoffs as a team that went from the Wild Card to the Super Bowl did. Furthermore, a team that wins two home games and the Super Bowl would earn nine points; a team that won three road games but lost the Super Bowl would receive the same figure. I don't think it's outlandish to suggest that both of those teams played very well. The maximum number of points a team could receive would be 14, which Pittsburgh achieved last year; the minimum, obviously, would be 0. 40% (44) of the teams who've made it to the playoffs over the last nine years (108) have not earned a single point.

After compiling the Playoff Score Points for each playoff team since 1997, the numbers were then correlated against seventeen of our metrics: Offensive and Defensive DVOA (both weighted and overall, as well as rushing and passing-specific numbers for both), Special Teams DVOA (again weighted and overall, as well as the individual kicking/punting unit statistics), and finally, Overall and Weighted DVOA. What did I find?

In short, that team defense rules the roost and a team's momentum ending the season has no effect in the playoffs. Take a look at these correlation coefficients:


Offensive Performance   Defensive Performance
Overall DVOA 0.069   Overall DVOA -0.225
Weighted DVOA 0.051   Weighted DVOA -0.226
Passing DVOA 0.062   Passing DVOA -0.174
Rushing DVOA 0.075   Rushing DVOA -0.242

(Remember that the defensive correlations are working with performance metrics where a negative number is preferred, so an inverse correlation would actually be preferable.)

As you can see, defensive performance is a stronger predictor of playoff success than offensive performance across the board. While the defensive figures aren't an exact correlation or close to it, remember that the small sample size of the NFL, even across the 16-game regular season, does normally result in lower coefficients and more variability than in other sports. In addition, a team's weighted DVOA is no better at predicting playoff performance than its DVOA over the course of the season as a whole. Overall, a team's DVOA over the course of the entire season (.317) had a stronger correlation with playoff success than its weighted DVOA (.264).

(Ed. note: Originally here there was a whole section about teams on five-game winning streaks not winning Super Bowls, except we apparently did something wrong with the research and missed a couple of streaks, so I just took it out. Nothing to see here. -- Aaron)

With regards to special teams, while having good special teams clearly doesn't hurt, it was surprising to find what particular unit didn't really matter:


Special Teams Performance
Special Teams Overall DVOA 0.177
Punt Returning 0.169
Punting 0.153
Special Teams Weighted DVOA 0.133
Kick Returning 0.115
FG/XP 0.041
Kicking -0.001

That's right -- apparently, having a good field goal kicker and/or a good kickoff man is entirely irrelevant to playoff success. This seems to jibe with Aaron Schatz's research in the New York Times about the lack of consistency in kicker performance on field goals.

(Ed. note: Then again, the same article pointed out that kickoff distance is one of the most consistent stats in the league, so I don't know if that article and this one are really related -- Aaron)

OK, let's summarize so far:

  • A good defense is important, specifically a good run defense
  • A good offense doesn't mean very much
  • A kicker's regular season performance means nothing for the playoffs
  • A team's end-of-season momentum isn't as important as it might seem

While those are some good overarching principles, there's more to be said about predicting postseason performance. In their piece, for example, Nate Silver and Dayn Perry pointed out that pitching is more important than hitting, but specifically that having a good closer and a staff with a good strikeout rate is crucial.

What does Football Outsiders have that analyzes performance of the same level of precision? Well, how about the brand spanking new Football Outsiders Premium Stat Database? What's it got, you ask? Well, DVOA for each team during each season split about 45 different ways both offensive and defensively, that's what! It has each team's performance separated by down, distance, score gap, field zone, season split, home/road, and even close and late (for you Tom Brady fans out there) situations. Remember Bill James' Favorite Toy? This is my new favorite toy.

(Ed. note: The beta version of the Premium Stat Database available for free during this year's playoffs doesn't have all these splits in it yet, but this gives you an idea of what's coming next year. -- Aaron)

Bringing the splits into the discussion provide some talking points for analysis and some insight on the upcoming playoffs.

Offense

Splitting the offensive data gave even more credence to the idea that regular season offensive performance has little or nothing to do with playoff success. The strongest offensive correlation (Third Quarter DVOA, at .147) would be the 20th strongest correlation if it were a defensive stat. Other, seemingly random statistics join Third Quarter DVOA at the top of the list: Second-and-Medium DVOA, Red Zone Passing DVOA, DVOA in the "Middle" Zone, and Offensive DVOA at Home. The prevalence of these unrelated statistics as the "strongest" correlations would speak more to a small sample size than to any sort of predictive value.

Defense

On the other hand, the defensive splits reveal several fascinating aspects of what's consistent with playoff success, including items and ideas that are consistent with what we've found in analyzing season-to-season performance.

Case in point: The weakest correlation between defensive performance and playoff success? Third-and-long DVOA (at .110; remember that a perfectly accurate defensive metric would be -1, so this is actually a correlation of -.110), followed by Third/Fourth Down DVOA and Third-and-Short DVOA. In much the same way that success on third down isn't predictive of future success, the same holds for a team's postseason performance.

Another example? Well, FO's 15th Precept says, "Championship teams are generally defined by their ability to dominate inferior opponents, not their ability to win close games." (For more information, please read this article by Aaron from 2005.)

That follows, to an extent, in the playoffs. A team's defensive performance while winning a game by 9+ points (-.227) is almost exactly as predictive as a team's defensive performance in games that are close and late (-.230). While this doesn't represent a team's ability to get into situations where they'd be up by a large margin, it does display their ability to keep the score that way.

What correlates strongest with postseason success? Actually, how a team does on first down:


First Down Passing DVOA -0.293
First Down DVOA -0.291
Road DVOA -0.258
Close & Late DVOA -0.230
Winning by 9+ DVOA -0.227
Red Zone DVOA -0.226
Games 10-17 Rushing DVOA -0.221

These correlations are significantly stronger than those on the offensive side. The data seems to point to two skills being predictors of post-season success:

  • Stopping opposing offenses on first down, particularly through the air (the correlation for first down rushing DVOA is lower, -0.137).
  • Shutting down the opposition's attack in the red zone, holding them to a field goal or preferably, no points at all.

The prevalence of Road DVOA being important can be considered a form of selection bias -- after all, teams who have the highest Playoff Score Points will have played well on the road -- but this shows that there is some predictive ability for regular season DVOA on the road when it comes to the playoffs. Well, on the defensive side at least; the correlation between PSP and Offensive DVOA on the Road is a measly .018.

Now, the important question: What does this all mean for the 2006 Playoffs?

Obviously, a greater correlation between defense and winning championships doesn't mean that an offense-first team CAN'T win the Super Bowl. But given the lack of any reliable or significant relationship between offensive performance in the regular season and playoff success, it's hard to recommend teams like Indianapolis, New Orleans, the New York Jets, Seattle, or Dallas.

Now, you might argue that Dallas' defense (16th in DVOA) doesn't belong in a group with the rest of those teams. When it comes to looking at their overall defense, perhaps; but once you break the unit's performance down into its particular splits, it reveals that Dallas is the team most uniquely suited for a failure in the postseason.

Remember that list of the ten strongest correlations between defensive performance and playoff success I listed above? Here's how the Dallas defense ranks in each of those categories:


Category Rank
First Down Passing DVOA 31st
First Down DVOA 30th
Road DVOA 14th
Close & Late DVOA 23rd
Winning by 9+ DVOA 6th
Red Zone DVOA 23rd
Games 10-17 Rushing DVOA 15th

As you can see, Dallas has a terrible defense on first down (they are above-average on third down), and is poor at stopping teams inside the red zone. Not even Carrie Underwood and a delicious hamburger can help that.

Let's look at the top seeds in each conference, along with that defensive juggernaut in Baltimore, and one mystery team:


Category BAL CHI SD ???
First Down Passing DVOA 8th 14th 9th 1st
First Down DVOA 3rd 13th 8th 2nd
Road DVOA 2nd 3rd 12th 7th
Close & Late DVOA 2nd 3rd 5th 4th
Winning by 9+ DVOA 1st 7th 23rd 8th
Red Zone DVOA 1st 12th 32nd 3rd
Games 10-17 Rushing DVOA 3rd 6th 28th 19th

The team whose shit might, in fact, work in the playoffs? The New England Patriots. They do extremely well in each of these categories except for rushing DVOA over the second half of the year.

Does this mean the Patriots are the favorites? No. They're still most likely going to have to play a playoff game at either San Diego or Baltimore, and that could very well be too much for them to overcome. But if they do make it through the AFC minefield and are hoisting up the Vince Lombardi Trophy on February 4th, well, you can tone down the platitudes about respect from Rodney Harrison and Tom Brady's clutch gritty manly leaderness by the media and tell your friends that the Patriots are a team just built for the playoffs -- and that you knew all along they wouldn't be facing Dallas.

(As a final note, I want to point out one of the interesting ramifications of this research. We previously discovered that defense varies from year to year more than offense does. Combine that idea with this idea and you are left with a dilemma for general managers: Focus on offense, and your team is more likely to be in the playoff hunt every year -- but less likely to actually win it all. Which is more important -- getting into the tournament, or having a better chance to win it once you get there? I'm sure we'll be continuing this conversation in Pro Football Prospectus 2007. -- Aaron)

Posted by: Bill Barnwell on 04 Jan 2007

168 comments, Last at 09 Jan 2007, 7:16pm by Pat

Comments

1
by RF (not verified) :: Thu, 01/04/2007 - 2:31pm

I haven't read the article yet, but I wanted to say that based on the title ... to paraphrase Cameron Crowe ...

You had me at s--t. You, had, me, a, s--t.

2
by Harry (not verified) :: Thu, 01/04/2007 - 2:40pm

If you are a GM or a coach I think there is no question that it is more important to build a team that can get into the playoffs than to build a team to win once you are there, at least if you're worried about job security.

3
by Athelas (not verified) :: Thu, 01/04/2007 - 2:40pm

Wow, as a Patriots fan, you give me some hope!
But it makes me fear Baltimore the most.

4
by Jimbo (not verified) :: Thu, 01/04/2007 - 2:42pm

Not sure why they weren't included, but the 2000 Ravens finished the regular season on a 7-game winning streak.

5
by kal (not verified) :: Thu, 01/04/2007 - 2:43pm

Typical FO New England Homerism.

:)

Great article. It's interesting how much Baltimore is favored over SD using this system, but more interesting is how dominant NE is here.

Where does NO rank? Heck, can we get the splits for all the teams and what their overall "SB worthiness" is?

6
by TheWedge (not verified) :: Thu, 01/04/2007 - 2:45pm

Is there anyway we can see the stats (as in the ones that correlate to playoff success listed above) for the other playoff teams?

7
by admin :: Thu, 01/04/2007 - 2:48pm

Sorry, Bill missed the Ravens... will add. Just to make sure people understand: This doesn't tell you who WILL win, it tells you who might have a better chance than their overall DVOA or win-loss record might indicate. And of course, we're not saying this is set in stone or that this is the last time we'll look at this research.

8
by Ilanin (not verified) :: Thu, 01/04/2007 - 2:54pm

Wow. Nice work, Bill. You've come up with the a solid statistical basis for "Offense wins games, defense wins championships" here.

Of course, something confuses me about the offense/defense logic here. The teams which are best known for coming up short in the playoffs in recent seasons are the Colts, Eagles and Steelers. The Colts certainly fit the model. The Steelers equally obviously don't - they've been a consistently strong defensive team who were generally torpedoed by quarterback play worthy of Rex Grossman. The Eagles haven't been (according to DVOA, anyway) consistently stronger on one side of the ball than the other under Andy Reid.

This is probably just small sample size, though. Specific examples don't work so well.

9
by Joshua (not verified) :: Thu, 01/04/2007 - 2:56pm

Nice article, Bill.

I agree that it would be neat to see the stats for all the playoff teams--I bet Philly looks really good.

10
by Purds (not verified) :: Thu, 01/04/2007 - 2:58pm

Ahhhhh!

Another long year as a Colts fan living in New England?! I can see it now...

Please say you're just kidding...

11
by Andrew Foland (not verified) :: Thu, 01/04/2007 - 3:00pm

When you measure a correlation coefficient from a sample of data, it comes with an uncertainty. Offhand I'd guess most of the uncertainties in the coefficients measured here are on the order of +-0.10, though you should be able to calculate it directly from the data you have.

When you have many quantities, all with significant uncertainties, and then you choose the largest or smallest of the quantities, you often end up looking at noise. I imagine that, for instance, the difference observed between the effect of first down DVOA and red zone DVOA is probably small compared to the uncertainties on both of them. (Though you can calculate and tell me if I'm wrong.)

On the same note, how statistically significant is the observed difference of 0.156 between defensive and offensive correlation?

12
by Tones (not verified) :: Thu, 01/04/2007 - 3:00pm

Didn't the NE Pats also go on a 9 game streak to finish 2001?

13
by Viva Pedro (not verified) :: Thu, 01/04/2007 - 3:01pm

Nice article. I'm feeling OK about my Baltimore wins it all prediction now. They beat your dark horse New England team in 5/7 defensive metrics. I don't think Rivers will perform nearly as well as he did early in the year. His arc this year will be very similar to Big Ben's first dramatic tragedy in the playoffs. They'll win a tight game against the Pats and then fall to the more experienced Ravens in the championship. I'd buy into the Pats darkhorse theory, but they didn't handle Jason Taylor well at all and will be unable to stop Merriman.

No NFC team will be able to stop the Ravens.

14
by TheWedge (not verified) :: Thu, 01/04/2007 - 3:02pm

#8
The Steelers/Eagles could have just been unlucky and run into better teams. They could have just been the second best team every year.

15
by Boots Day (not verified) :: Thu, 01/04/2007 - 3:06pm

To look at this on a more macro level, no team has won the Super Bowl without winning at least 11 regular season games since the 1988 49ers, who won 10. Since the NFL went to a 16-game schedule, they're the only Super Bowl champ with fewer than 11 regular-season wins (aside from the 1982 Redskins, who went 8-1 in a strike-shortened season).

If that holds, the only teams with a shot at winning the Super Bowl this year are the Chargers, Ravens, Patriots, Colts and Bears. The Bears are the only NFC team that even has a chance, which I think is probably not such a controversial notion.

16
by Steve (not verified) :: Thu, 01/04/2007 - 3:13pm

Nice work. Just took a look this morning and the DVOA's for the Super Bowl teams since 1997. The losers on average actually had better offenses than the winners, but the winners had much much stronger D's. Only the '03 Pats (in one of the biggest upsets of all time) and the '98 Broncos (with a pretty darn good offense) won the Big One with a D rated lower than 6th overall.

17
by Pat (not verified) :: Thu, 01/04/2007 - 3:16pm

When you measure a correlation coefficient from a sample of data, it comes with an uncertainty.

Not without either a resampling technique (see here) or the assumption of normally-distributed data, which is almost guaranteed to be wrong (only teams which reach the playoffs are involved - therefore, there's a cut on things which lead to regular season wins).

Using the bootstrap resampling tool on that page would probably be an interesting idea, but the small size of the data set might limit things.

18
by Pat (not verified) :: Thu, 01/04/2007 - 3:18pm

#14: Like the Colts, in 2003, 2004, and 2005, who lost to the Super Bowl winner in the playoffs every year.

19
by joel in providence (not verified) :: Thu, 01/04/2007 - 3:22pm

as a fan, i'm all for the "make the playoffs every year" school of thought. "flukey" teams that put up a great record and then drop right back down the next year get no love!

20
by navin (not verified) :: Thu, 01/04/2007 - 3:26pm

I think once you add in teams going back to the early 80s offensive DVOA will become more important.

Nine years is a really small sample size, and the failures of Indy and maybe Philly make offense look less important than it might actually be.

Some really impressive offensive teams won or reached the Super Bowl in the 90s and 80s but the 00s have been dominated mostly be defensive team. While I really like the idea presented by this article, I don't know how confident we can be in the actual numbers.

21
by James G (not verified) :: Thu, 01/04/2007 - 3:27pm

Good article, but I must jump in with my English pet peeve:

This research doesn't "jive" with Aaron's research. This reasarch, however, might jibe with Aaron's research.

22
by joel in providence (not verified) :: Thu, 01/04/2007 - 3:28pm

also, weren't the 2004 eagles AND steelers both among the top all-time teams in DVOA? yet both were unlucky to have the 2004 patriots at their absolute peak.... god 2004 was just bananas for football fans.

23
by B (not verified) :: Thu, 01/04/2007 - 3:30pm

"Which is more important — getting into the tournament, or having a better chance to win it once you get there?"
Flags fly forever.

24
by bmw1 (not verified) :: Thu, 01/04/2007 - 3:32pm

I'm confused as to why you point out that the Patriots are the team that is best built for the playoffs when the Ravens rank better than them in 5 of the 7 categories, and are only one spot behind them in another. Homerism?

25
by Pat (not verified) :: Thu, 01/04/2007 - 3:32pm

Bill:

Speaking of uncertainty, though, part of the problem you've got here is that your data points aren't necessarily independent. The Patriots, with Adam Vinatieri, have had bad kickoff DVOAs in 2001, 2004, and 2005, and they were 'meh' in 2003. That's because Vinatieri isn't that good a kickoff kicker. That's one data point you're treating as four, and given that the Patriots won the Super Bowl in 3 of those years, and earned 2 points in 2005, that could be a big part of the reason why the kicking DVOA has such a low correlation.

Think of it this way: because some of the points with the biggest lever arm (NE 2001, 10 points, NE 2003, 9 points, NE 2004, 10 points) all have poor kicking DVOA, the correlation says "hell, kicking DVOA doesn't seem to matter" whereas all it's really saying is "Adam Vinatieri's kickoffs didn't hurt the Patriots" - but that could easily be coming from something else (all the defensive metrics) rather than any intrinsic unimportance of kicking.

26
by turbohappy (not verified) :: Thu, 01/04/2007 - 3:33pm

Really interesting article and the Stat Database is going to be awesome.

Since the article kicks off with Polian, can I get the Top 7 Playoff Stats for the Colts? I suspect that they are not nearly as bad as you'd expect, probably better than Dallas.

27
by B (not verified) :: Thu, 01/04/2007 - 3:38pm

24: It's because the ratings in the top categories are more important than the ratings at the bottom categories. Also, Bill is a Giants fan, so we should all feel bad for him.

28
by Frick (not verified) :: Thu, 01/04/2007 - 3:43pm

Re: 23

And if don't get into the play-offs you don't have a job if you are the coach or GM.

If you are the owner in a some markets you aren't making money.

I'm a Colts fan, and I while I hate the fact, I'm realistic enough to realize that the Colts are built to attract people to the games. How do you do that? By winning games and generating hype and excitement.

I'm sure that Irsay and other owners wish they were in markets where they could field an awful team and still sell out. The Packers are a small market team that sells out consistently, but from what I've heard from friends who live in WI is that Packers tickets while still not easy to get are noticebly easier to obtain than they were when they were a play-off team.

29
by turbohappy (not verified) :: Thu, 01/04/2007 - 3:43pm

Interesting stat from the Stat Database for the Colts defense:
Q1: 16th
Q2: 30th
Q3: 15th
Q4: 31st

Correlates with my assertion that there's not as big of difference between this year and last year as it seems - last year they were just enough better in Q1 that they didn't get tired in Q2.

30
by Chris (not verified) :: Thu, 01/04/2007 - 3:45pm

Any comments on exactly why this would be the case?

With baseball, there are many tangible differences between 162 games and seven games. In a seven game series, you can be do or die with your pitching staff, play your best starter three times a la Jack Morris, etc. Good pitching beats good hitting in the playoffs generally because you can give an otherwise unsustainable number of innings to your best pitchers. All those good hitting stats were racked up playing against 6 innings of good pitching and 3 innings of mediocre pitching a game. It's different facing nine good innings a game. Anyway, you see where I'm going with this. How is playoff football that intrinsically different?

In football, that doesn't seem to be the case. Football games are pretty do or die. Fatuous Bill Simmons theorizing nothwithstanding, I don't think that teams do "Milton Berle" games during the season, "saving" themselves for the playoffs. The whole Guts and Stomps thing tends to point this way as well.

So, I guess you can color me unconvinced, at least initially. With only the 9 years of data, this could be pushed along by the Pats dynasty (which was also an outlier in the Guts and Stomps thing). Here's a thought, though--could the whole cold weather advantage thing be the real driving force behind this? If cold weather teams tend to be more defensive oriented (I don't know if this is the case, but it doesn't seem outlandish), then those teams would be overperforming in January, and would have more postseason success.

Anyway, I really enjoyed this article, just trying to think things through.

31
by steelberger1 (not verified) :: Thu, 01/04/2007 - 4:00pm

re 12:

It was 6 games I think, but should still be included.

32
by Rocco (not verified) :: Thu, 01/04/2007 - 4:00pm

"Which is more important — getting into the tournament, or having a better chance to win it once you get there?"

I want a team that will get to the playoffs consistently and hope that one year the matchups break my way and/or luck is on my side. If you believe (like I do) that playoffs are a crapshoot, then you want to be in the postseason as often as possible. Building a great playoff team isn't all that helpful when you're watching the playoffs from your couch.

33
by steelberger1 (not verified) :: Thu, 01/04/2007 - 4:02pm

re 12:

It was 6 games I think, but should still be included in the article.

34
by Rob (not verified) :: Thu, 01/04/2007 - 4:04pm

That's "predictive" not "predicative".

35
by steelberger1 (not verified) :: Thu, 01/04/2007 - 4:04pm

I wonder how the winning streak theory would work if the last game wasnt included when teams had no chance to improve their seed (i.e. resting players).

36
by steelberger1 (not verified) :: Thu, 01/04/2007 - 4:06pm

Ask the 2001 Steelers if special teams matter in the playoffs....it hurts just to remember it.

37
by Marko (not verified) :: Thu, 01/04/2007 - 4:09pm

"This seems to jive with Aaron Schatz’s research in the New York Times about the lack of consistency in kicker performance on field goals."

That should be jibe, not jive. As Barbara Billingsley might say, "Jive ass fool don't got no brains anyhow." (Sorry, I couldn't resist.)

38
by admin :: Thu, 01/04/2007 - 4:09pm

It seems Bill may have messed something up on the winning streaks. I've e-mailed him about it but he's on vacation, I'm going to wait for him to fix it so we make sure we don't miss any. No need to keep bringing up examples; we know it's an error. I'll change the word "jibe" too. This is what I get for editing an article myself instead of handing it over to Tim Gerheim.

39
by Marko (not verified) :: Thu, 01/04/2007 - 4:13pm

#21: I didn't see your post before my post - I hadn't refreshed my screen for a while. Obviously, we have a similar pet peeve.

40
by econometrician guy (not verified) :: Thu, 01/04/2007 - 4:17pm

For large samples, you can compute the standard error of the correlation coefficient without using resampling or assuming normality.

41
by Pat (not verified) :: Thu, 01/04/2007 - 4:52pm

For large samples, you can compute the standard error of the correlation coefficient without using resampling or assuming normality.

Considering football stats live in the world of 16-game seasons, there's a reason why I ignored that possibility. 68 points distributed from 1 to 14 isn't a large sample.

42
by Countertorque (not verified) :: Thu, 01/04/2007 - 4:53pm

With that database available, I may never work again.

43
by Scott C. (not verified) :: Thu, 01/04/2007 - 5:13pm

Considering only 5 game win streaks is not enough.

Consider 10 game winning streaks at the end of the season and look again.

Somewhere between 5 and 10 game winning streaks at the end of a season, the correlation with playoff prowess grows dramatically.

44
by elibolender (not verified) :: Thu, 01/04/2007 - 5:14pm

Love the hamburger quote. That's high comedy there.

45
by bsr (not verified) :: Thu, 01/04/2007 - 5:17pm

#30 - I was thinking along the same lines at first. That Pats represented nearly 5% of the sample population and would probably skew the results in a way to point to them as having one of the stronger correlations. As I began to think of the specific teams, however, I realized that none of the Patriots teams are really all that similar in what their player makeups and strengths were.

By the way, nice thought provoking article. I also would love to see a larger population, but I don't know how reliable those would be given rule changes and the like. Is there a point in time that FO would be hesitant to "mix" data from one era to the next? The start of free agency would probably one of those dates. The change in the pass interference rules would have to be another.

46
by Bobman (not verified) :: Thu, 01/04/2007 - 5:22pm

Purds,

Come on, it's not like it's a surprise.

Turbohappy, that Dfeensive DVOA variance from quarter to quarter is actually predictable for small fast guys but potentially good news. If Indy does play according to the script and the O gets a lead, their 15th ranked D will not necessarily face 10 runs on a 12-play drive and tire out like they do. If they can keep the opponents to a roughly 50/50 run/pass balance, I bet their 2nd and 4th qtr D rankings rise to, maybe 20-22.

Yes, compared to Baltimore it's laughable and I am grasping at straws, but a defensive DVOA of 15/20 from quarter to quarter might be all they need. I sure as hell know that 15/31 is NOT what they need.

And Pat, this might be the 4th year in a row Indy loses to the eventual SB champ. Some claim to fame. They're Buffalo Junior. Odds favor it if they lose to either Balt in Balt or beat them to face SD. And if they win it all and break the streak, well, what was the title of that Bill Simmons book a couple years ago....?

47
by Jimbo (not verified) :: Thu, 01/04/2007 - 5:22pm

#42 - I'm wondering if we can get a thread devoted to nuggets we've dug out of the data base. Seeing that the Colts have the #1 first half offense and the Chiefs have the #31 first half defense makes me wonder if Indy will put the game out of reach early.

And the Ravens third quarter D is incredible. Rex Ryan must be making some kind of halftime adjustments -- why isn't he getting mentioned as possible head coach material?

48
by Go Chargers (not verified) :: Thu, 01/04/2007 - 5:24pm

As a Sociology major, I have learned there are three types of lies: lies, damned lies and statistics.

Clearly FO forgot to include the statistical impact of running backs wearing No. 21 in blue and white and the likelihood of a former basketball player catching touchdown passes as a tight end.

I added these to FO's calculations, and the clear cut Super Bowl winner is the Chargers.

Trust me on this...I'm edumacated.

GO CHARGERS!!!

49
by throughthelookingglass (not verified) :: Thu, 01/04/2007 - 5:33pm

I'm looking at the premium stats database-Thank You Aaron!-and the Colts' offense has a 175.3% DVOA on third and long? How is that even possible?
That would explain why Peyton-Reggie-Marvin's DPAr are so high. 175.3%? Wow.

50
by Andrew (not verified) :: Thu, 01/04/2007 - 5:39pm

Viva Pedro #13:

No NFC team will be able to stop the Ravens.

That's not the real question. Its not whether the Ravens can be stopped - clearly their pop-gun offense can be stopped. Its whether the NFC team can find a way to get something going against the Ravens defense before the defense forces them into a costly mistake. The "weakest" point on the Ravens statistically is runs middle/guard and off right tackle, passing to Tight Ends, and passing to #1 (hello Samari!) and other wideouts. Just a cursory check suggests their worst NFC match-ups would be the Eagles and Giants offensively, since those "weaknesses" are the offensive strengths of those two teams.

51
by Mike (not verified) :: Thu, 01/04/2007 - 5:44pm

I hate to ask this because it seems so cheesy but given we only have nine years to work with ..

What are the correlations if you remove some of the most obvious, cliche examples of each of these (IE, Colts being offense heavy and failing alot, do non-Colts teams with good offense correlate noticably better? Do defense-first teams only correlate well because of Baltimore and Tampa Bay? Do all those things the Pats do well only correlate highest because they've done them well and won alot of games the last few years?)

It seems like such a small sample size is prone to heavy adulteration by the specific examples because some of these teams have been involved every year. Naturally anything the Pats have done consistantly well through their run will correlate well with playoff success. But that doesn't mean it does universally - if it doesn't correlate at least somewhat with them omitted, then it's very possible they adulterate the sample.

Of course, you knew this, but I'd like to see myself anyway.

52
by Dave Brude (not verified) :: Thu, 01/04/2007 - 5:50pm

A breif early 90's rundown of Superbowl winners

1990 Giants- Powerhouse defense with very low turnover (only 5ints on 311 attempts) but effiecient passing game and grind it out running game

1991 Redskins- Led the league in pass offense and pass defense in YPA. Near league leaders in lowest int% on offense and highest int% on defense. Run game wasn't great on offense but it didn't need to be and held onto the ball. Had many stomps 260 pt differntial with only 224 pts allowed

1992 1993 1994 1995 Cowboys Niners- Cowboyw won 3 out of the 4 Superbowls but the Niners were right there with them Again these teams were dominant on both sides of the ball.

I think Indy has a chance if they can generate some INT's with their pass defense but I wouldn't make them the favorites. I think it's a crapshoot between NE, BAL, and SD with INDY having an outside shot if they can get a few good games out of thier defense specifically in the INT or fumble dept. Thier pass defense isn't terrible just mediocre.

53
by Dave Brude (not verified) :: Thu, 01/04/2007 - 5:50pm

A breif early 90's rundown of Superbowl winners

1990 Giants- Powerhouse defense with very low turnover (only 5ints on 311 attempts) but effiecient passing game and grind it out running game

1991 Redskins- Led the league in pass offense and pass defense in YPA. Near league leaders in lowest int% on offense and highest int% on defense. Run game wasn't great on offense but it didn't need to be and held onto the ball. Had many stomps 260 pt differntial with only 224 pts allowed

1992 1993 1994 1995 Cowboys Niners- Cowboyw won 3 out of the 4 Superbowls but the Niners were right there with them Again these teams were dominant on both sides of the ball.

I think Indy has a chance if they can generate some INT's with their pass defense but I wouldn't make them the favorites. I think it's a crapshoot between NE, BAL, and SD with INDY having an outside shot if they can get a few good games out of thier defense specifically in the INT or fumble dept. Thier pass defense isn't terrible just mediocre.

54
by Bill Barnwell (not verified) :: Thu, 01/04/2007 - 6:16pm

Hey guys,

I'm on a real crappy computer filled with spyware at the MGM Grand so I can't answer questions too thoroughly. When I get back, I'll be able to do some more research on the questions that have come up.

Just a few quick notes:

- I'M SORRY about the jive/jibe thing. I am ashamed of myself and my family isn't too proud of me either.

- The reason the Ravens didn't come up as winning their last five games, even though they did, was because I was only looking at games 13-17 and the Ravens had a bye. That's my bad -- I should've stated that. I would imagine that the traditional idea of "momentum" would consider a bye week to be something that impedes that momentum, but I think that's something we can look at in the future, too.

- I really wish this Bonzi Buddy would go away.

- Obviously the small sample size does play an issue in complicating the reliability of the findings. I'm not worried so much about teams repeating with the same core group of players because they'd be representing 4 or 5 of 110 teams, and if the Patriots win so much despite not having a solid kickoff guy, it would then follow that a kickoff guy wouldn't be that important! Otherwise, the Patriots wouldn't have won. I don't think that logic is fallacious but I'm quite hung over.

55
by Oswlek (not verified) :: Thu, 01/04/2007 - 6:18pm

One other thing about the streaks. Adding NE to the list, 7 of 14 made it to the big dance. 11 of 14 made it to their conference championship.

When I read that chart, I find a streak to be a whole lot more meaningful that Bill did.

Otherwise, I think it is one of his better pieces.

56
by joel in providence (not verified) :: Thu, 01/04/2007 - 6:21pm

that 1991 redskins offense was positively bonkers. maybe this is just my selective memory but i seem to remember rypien comleting an absurd number of long td passes. like he'd have 3 or 4 BOMBs per game.

57
by Andrew (not verified) :: Thu, 01/04/2007 - 6:22pm

The basic gist of "defense wins championships" can be seen statistically in the Pythagorean Wins formula.

The Super Bowl winner has been the Pythagorean Win leader in 10 out of the past 16 years. The #2 team won in another 2 of those years.

The Pythagorean Win formula mainly varies with changes in points scored against, which is primarily affected by defense. Scoring 50 more points in a year is far less important than preventing the scoring of 50 more points.

For example, a 400-300 team has a Pythagorean Win of 10.24. If they go 450-300, it rises to 11.08. But if they go 400-250, it rises to 11.51.

If a higher Pythagorean Wins total is predictive of Super Bowl victory, defense is far more important, which is also why we see so many Super Bowl champs be among the top 6 in preventing scoring. The only recent champ not in the top 6 in preventing scoring was the 98 Broncos, and they were 7th.

58
by hgfalling (not verified) :: Thu, 01/04/2007 - 6:37pm

Why again are the five-game winning streaks not predictive when twice as many teams won the super bowl as would be expected if all playoff teams were random, and *half* the teams made it to the SB?

59
by Jimbo (not verified) :: Thu, 01/04/2007 - 6:40pm

The 91 Redskins outscored their opponents by a more than 2-to-1 margin for the season (485 to 224). And I think their sack differential was more than +40, in large part because Rypien was sacked 9 times all season. The Ravens have a +43 sack differential this year, which is pretty amazing.

60
by Bobman (not verified) :: Thu, 01/04/2007 - 6:45pm

Mike #51, I wondered about this too--if you take out the frequent outliers (Indy on O and TB/Balt on D) do the numbers stand up? I suspect they do--think the year Oakland faced TB in the SB. D won big-time. Can't blame it all on Barrett Robbins.

Dave #53, keep in mind Indy's D has faced the fewest passes of anyone, so they may be mediocre, or they may be worse if seriously challenged. I doubt Brady will throw 5 picks against them again (did he really throw 5? And NE only lost by one TD?) They are currently playing safeties that rank 5 and 6 on the depth chart, and even with Sanders back, he's not 100% and not exactly a cover guy.

Bill Barnwell, thanks for your dedication, emailing from vacation and while hung over to boot! The true sign of a great professional.

61
by jacob (not verified) :: Thu, 01/04/2007 - 7:12pm

I'm pretty skeptical of the all the stats presented here. None of those correlation coefficients are significant. Most show downright zero correlation, suggesting that Billy Beane's theory, if applied to football, is correct.

The only thing that looks at all statistically relevant is the momemtum thing, which you discounted. Despite the incredibly small sample size. 3/13 teams won the superbowl with momentum and only 6/95 won the superbowl without momentum. If you are going to make a claim about those numbers either way, it seems to me to have to be that momentum is the only statistically relevant stat going into the playoffs.

And look one further, 7/13 teams entering the playoffs made it to the superbowl. which means only 11/95 teams without momentum made it to the final match.

Here's the study, using your methodolgy. Rank all playoff teams from last 9 years by winning percentage over last 5,6, and 7 games. Now rank all playoff teams from last 9 years based on your playoff points system. Find the correlation between the rankings, i'll wager it blows all the DVOA correlations out of the water.

Why? Cause your performace over the last half of the season is far more relevant than your performance over the entire season. How many hundreds of anecdotal bits of evidence can we find just within the NFC East this year...

:)

Cheers, i did enjoy reading it though, despite the doubting thomas-y-ness.

62
by billsfan (not verified) :: Thu, 01/04/2007 - 7:12pm

I'd like to see how some NFC teams lacking a QB named Grossman rank here. Like Philadelphia, for example, who seems like the only team in the NFC with a chance. I know that their red zone D is boosted by a ridiculous number of stops and turnovers/TDs in "and goal" situations, but your database software crashed before I could look up any stats on my own.

63
by Mike (not verified) :: Thu, 01/04/2007 - 7:16pm

I agree the logic's not totally fallacious, but I suppose I'm just getting stuck on the smallness in absolute terms of the correlations we're dealing with - it's just so realistically possible that the Pats or someone else won despite x or y and not because of it due to the sample size, and I would think that any team that's advanced in the playoffs 2-3 times would represent a significant sample because 40% of the teams were 1 and dones, after all.

With all that said, I really enjoyed the article, I just wonder how profound the stilting effect is of those most successful teams.

64
by BD (not verified) :: Thu, 01/04/2007 - 7:20pm

I think others have mentioned it, but the statistics professor in me advises everyone to treat the splits with caution as it involves many comparisons therefore raising the chance of a spurious result. (especially with a sample size too small to support it)

But the results seem to make some sense. Imagine good offense vs. good defense. For the offense to score, they must either sustain a drive against a defense that does not allow sustained drives, or they must get really lucky. The defense makes one or two pretty good plays at any point in the drive and they get off the field. Good offense must count on a string of successes to score (or a lucky bomb).

65
by BD (not verified) :: Thu, 01/04/2007 - 7:26pm

To be fair in interpreting the results, consider that we're talking about the outcome of a couple 60 minute contests. Random error is bound to be there (Bills fans... can you say wide right?).

The article doesn't address statistical significance per se, but a significant correlation around .2 or .3 is definately NOT zero! In some fields, a correlation of .3 can be considered a fairly robust effect. With all the bounces of the ball, snowy Januarys, tuck rules, etc. I would say a .25 correlation is meaningful.

66
by zlionsfan (not verified) :: Thu, 01/04/2007 - 7:27pm

Bobman, it was "Now I Can Die In Peace", written by the guy who a) "created" the five-year moratorium and b) promptly broke it about 5000 times with respect to the Red Sox, so take that with a grain of salt. (It's not a bad book, but if you can't read all the way through some of his columns, I'd skip it.)

It's one thing to say that a team like the Colts should make a change to shoot for one big flag instead of a number of little ones (you know, they put up flags for everything these days, and I mean everyone, not just the Colts or just NFL teams), but sometimes you make a change and end up running the franchise into the ground because you hired a completely incompetent individual and refuse to acknowledge it, and what's worse, not only does he refuse to acknowledge he's incapable, he thinks it's some badge of honor to be terrible at your job but to keep on doing it anyway, as if years of sucking would suddenly make you good. (Yes, the Lions were kind of in that position - not as good as the Colts, obviously, but six playoff appearances in the '90s and one NFC title game appearance was a hell of a lot better than the decade before or the decade after.)

I don't think more variance in defense means that you're better off building your team around offense. I think it means that you have to focus more on expected value of your defense than actual value: it's more likely that your offense really is bad if it has a bad year than that your defense really is bad if it has a bad year. Or, to put it in playoff terms, if you have a mediocre defense, it might need a bit of help or a lot of help, but you shouldn't necessarily clean house - you should try to swap out bad parts for better parts and wait for it to gel. On the other hand, if you have a mediocre offense, it probably is what you think it is, but even if you make it better, you won't necessarily go farther in the playoffs.

67
by Pat (not verified) :: Thu, 01/04/2007 - 7:42pm

None of those correlation coefficients are significant.

The size of a correlation coefficient does not have anything to do with its significance. Its significance is determined by more complicated measures (most people think of p-values, but in this case, getting a p-value from a chi-squared is probably not accurate at all).

You can have small but significant correlations. It happens all the time.

I’m not worried so much about teams repeating with the same core group of players because they’d be representing 4 or 5 of 110 teams,

Bill:

The Patriots don't represent 4 or 5 of 110 teams. They represent 3 out of 8 teams that have won the Super Bowl - which is a much bigger sample - and teams that have won the Super Bowl, by definition, dominate the large-value of Playoff Score Points.

Think of it on a graph: the Patriots (well, Adam Vinatieri, obviously) represent three out of 8 points on the "large PSP" side of the graph. And they're all low, or negative. Even if all 5 of the other 8 Super Bowl winners had positive kicking DVOA (they don't), that would still look like a weak correlation. They have a lot of lever arm on the fit, and it's all due to one point.

and if the Patriots win so much despite not having a solid kickoff guy, it would then follow that a kickoff guy wouldn’t be that important!

Not necessarily - it could be that there's something else consistent about the Patriots over that time period that allows them to win in spite of poor kickoffs. That's the problem - it's basically one data point.

Then again, of course: the other Super Bowl winners' kicking DVOA were 6.6, -4.8, -0.7, 4.1, 9.3, and -1.6, or an average of 2.2. So it almost definitely doesn't matter anyway.

68
by billsfan (not verified) :: Thu, 01/04/2007 - 7:46pm

Never mind, it's working again.

As far as I can tell from the premium stat preview, the Eagles are 7th late and close (Saints 20th, Giants 22nd), 19th on first down (Giants 9th, Saints 14th), and 8th red zone (Saints 6th). FWIW, Philly was #1 in goal-to-go defense.

69
by billsfan (not verified) :: Thu, 01/04/2007 - 7:55pm

65:

Another good example is Kevin Dyson not having long enough arms. And I hate you.

70
by Lincoln (not verified) :: Thu, 01/04/2007 - 8:08pm

Great Article

71
by Yaguar (not verified) :: Thu, 01/04/2007 - 8:11pm

First, on the five-game winning streak subject:

DVOA correlates better with playoff success than weighted DVOA. That tells you that the results of early games are still relevant enough to be predictive.

But on the other hand, the teams that have gone on 5+ game winning streaks going into the playoffs have done spectacularly well. Why is that?

Well, if you're good enough to win five or more games in a row, then you're probably a really good football team. A team that has a five-game winning streak probably went 11-5 or 12-4, minimum. Of course that sort of team is going to do well.

72
by admin :: Thu, 01/04/2007 - 8:12pm

I just took out the winning streaks thing. We missed a couple teams which won Super Bowls, which makes Bill's point look wrong, except that we also probably missed a couple teams that didn't win Super Bowls and nobody is bringing them up to make Bill's point look better, so frankly we should just re-do the whole thing at some point. The article works fine without it so just go about your business.

73
by stan (not verified) :: Thu, 01/04/2007 - 8:21pm

I was wondering if it was possible to do analysis of DVOA involving only teams with a winning record to see if any interesting trends develop.

The title of the article focuses on the Colts losses in the playoffs. In looking back over the last three years, why did they lose?

2003 and 2004 -- the Pats were superior in both lines. The wind was also a factor in 2003(never understood why people focus on cold when it was clearly wind affecting ball flight). The other thing that is obvious to anyone going back to look at those two games is that the Colt receivers could not get open. On defense, the Colts couldn't get a pass rush in 03 and couldn't stop the run in 04. Brady's failures were what kept the 03 game close and the 04 game close until the 2d half when the Pats finally took the ball away from him and pounded it every play.

In 05, Steelers just absolutely overwhelmed the Colt O-line. People focus on the blitz, but it wasn't a blitzing LB coming unblocked that created the havoc. It was all the Steeler pass rushers dominating their blockers. It looked exactly like a replay of the Charger game from the reg season.

So what is the "explanation"? The Colts play with the smallest margin of error of any offense. Their run is totally dependent on the pass. Their pass is predicated on having a WR/DB mismatch somewhere and the belief that wherever it is on the field, they (18) will find it and get the ball there (and before your unblocked blitzer can reach him). They don't need real good pass pro, barely adequate will do. They don't need wide open receivers, a tiny opening will do. They believe their offense can outscore what you do to their defense.

What is amazing over the last few years is that they can take barely adequate pass pro and small mismatches with WRs and put up 40 points. Even a slight improvement in pass rush &/or a slight improvement in coverage can just about shut them a down.

The problem -- their pass pro is barely adequate. If the pass rush from the def front four manhandles the O-line it all goes to crap. If the front four stops the run without help (see Jax, Tenn this year), they can get 7 defenders totally focused on 4 receivers. If the front also dominates with a pass rush, it gets really, really ugly.

When the Colts face big physical D lines with some ability to pass rush and decent secondaries, they get embarassed. Because they have no answer. They can't knock anyone off the ball. They can't win with defense or special teams. They absolutely must have a little time to execute the precision pass game because it is all they have to win with.

74
by jonnyblazin (not verified) :: Thu, 01/04/2007 - 8:27pm

re: 50
"Its not whether the Ravens can be stopped - clearly their pop-gun offense can be stopped. Its whether the NFC team can find a way to get something going against the Ravens defense before the defense forces them into a costly mistake."

First off, the Ravens offense has been a top ten unit since Billick took over, its hardly pop-gun. There are only 2 elite defenses in the playoffs, the Bears and the Ravens (the next team is NE at -8.3%), and the Bears D has been falling apart of late, so I don't see any team in the playoffs that could possibly shut them down.
What worries me is the punt and kick returns. Evers since B.J. Sams broke his leg, Cory Ross has been the return man, he's a pretty green rookie. I can definitely see him muffing a punt in a key situation. Clayton is probably a good return man but he hasn't seen any game action, so he is prone to making a mistake as well.
"The “weakest� point on the Ravens statistically is runs middle/guard and off right tackle"
The Ravens rank 2nd runs to mid/guard (3.78ypc) and 7th at right tackle (3.5ypc), but 1st at right end (1.99ypc). No area of the run D is weak, maybe a RB busted one long run off right tackle that skewed the average. I don't think coach watching tape would think running at RT would seriously exploit the Ravens D.
I think the problem with trying to attack Rolle downfield, where he's been burned several times this season, is that then the QB has to sit in the pocket for a while , and if that reciever is doubled or not open, the QB will likely be crushed by Suggs, Scott, etc. A team would need a real burner as a #2 reciever (assuming McCalister covers their best WR) to cause problems, the only team that really has that is the Colts. Of course, if the Ravens cover a teams best reciever with Rolle (see Lee Evans TD), then they are screwed.

75
by Chris (not verified) :: Thu, 01/04/2007 - 8:47pm

I agree with Pat. And, of course, there is a similar point with offensive teams in that the Colts, with their high powered offense, have consistently underperformed in the playoffs. Last year, they would have gotten zero PSP. And, like Pat's point, it's really one data point. It's basically been the same Colts offense for each of those seasons.

Kudos to Bill Barnwell for crunching the numbers, but I would have liked to have seen him posit a causal mechanism for why good defense would trump good offense in the playoffs. In baseball, a plausible one is fairly easy to identify, but I can't see why one aspect of a team's performance would overpredict in the playoffs.

76
by bsr (not verified) :: Thu, 01/04/2007 - 9:26pm

#73 - You are underselling the OL and WR of the colts by a large margin. Saying that they have barely adequate pass protection or wide recievers that barely get open is a gross understatement. Both are exceptional.

77
by ElTiante (not verified) :: Thu, 01/04/2007 - 9:29pm

A few thoughts on why defense might play a more significant role in recent NFL playoffs:
* Refs call fewer penalties in the playoffs, making it easier for defenses to disrupt timing of offenses (I realize last year might be an exception)
* Since LT (the original), the disparity in speed between offensive players and defensive ones has diminished. Montana and Rice played many more games vs. old-style linebackers and DEs (big, slow guys) than current "West Coast" offenses do.

Just a few thoughts... I'm not claiming any sort of substantiation other than defensive dominance in playoffs recently.

78
by RF (not verified) :: Thu, 01/04/2007 - 9:37pm

One thing missing from the article (please correct me if I'm wrong). It's nice to quote correlation coefficients, but are these numbers significant? At what level?

As a suggestion for further research, I think it would be interesting to assign dummy variables to things like "3-4 defense," "4-3 defense," "predominant Cover 2 scheme" and do a regression to try and determine significance between the points formula you mention and these factors.

In general, I would have liked to hear more discussion of why the factors you tested were chosen - I'm assuming it's a data thing. Perhaps doing some multivariate analysis of the factors you found most compelling?

79
by RF (not verified) :: Thu, 01/04/2007 - 9:51pm

Adding to my comment in #78, there may be a line editors want to walk with regard to the statistical methods and writing an article which needs to transcent the statistically inclined crowd. That sign, things like the level of significance are very important. Perhaps using tags and endnotes to say "significant at the X level" would be enough to have the information yet not detract from the article as written.

80
by David B (not verified) :: Thu, 01/04/2007 - 9:52pm

Some statistical quibbles...

First off, it is quite likely that the playoff score points system makes the correlation coefficients weaker. It would be instructive to rerun the analysis using a simple dummy variable approach with wins-losses as 1-0. This way victories in certain games by certain teams don't have more weight. If, for example, the last 9 superbowl winners all had excellent run defenses, the small sample size assures of biasing our statistic by using the weighted playoff score system. This is further exacerbated by using linear regressions and a non-linear point system.

Statistical quibble #2: "momentum" shouldn't be judged by wins\losses. Football Outsiders correctly understands that a team can lose based on bad luck. Instead, a teams DVOA growth rate (or stability at a high number) prior to the playoffs should be used. I understand that this introduces elements of a time series analysis into the picture, but really this would be much more accurate.

Quibble 3: Using linear regressions for playoff success is probably always going to yield low correlations. It is quite probable that the relationship is either log-linear or exponential, meaning that either small improvements at the low end are more important or small improvements at the high end are more important.

To understand 3, think about it this way: Is the difference between a team with a run DVOA of 0% and -5% more, less, or the same as a difference of -20% and -25%? One is the difference between an average defense and a slightly better than average defense, the other is the difference between a good defense and a best-in-the year, exceptional defense. There are many teams in the 0% to -15% range in any year, but few ever crack -25%. The result is that changes in DVOA at the extremes are likely indicative of something intrinsically 'more valuable' and need to be weighted more heavily by using an exponential model for the regression.

81
by Pat (not verified) :: Thu, 01/04/2007 - 10:06pm

Perhaps doing some multivariate analysis of the factors you found most compelling?

Hey, there's only 64 data points with non-zero "playoff score points" - eliminating additional degrees of freedom (especially when several of those data points are likely covariant, as I mentioned before) is just going to murder you.

It would be instructive to rerun the analysis using a simple dummy variable approach with wins-losses as 1-0.

Skip that. Why not just use DVOA in the playoffs itself? You've got a better measure of a team's performance in the playoffs. Why not use it?

82
by stan (not verified) :: Thu, 01/04/2007 - 10:11pm

76,

The Colts offensive line is barely adequate. They can't run block (in any ordinarily understood definition of the term). Check the FO stats and see that they always rank among the very worst in short yardage situations every year. They are absolutely pitiful if you need to pick up a yard and run a straight ahead power.

If you want to see how soft they are (and why Joey Porter called them out on it), watch the tapes of the SD or Pitt games last year or the Dallas, Jax or even Tenn game this year.

I don't believe I said anything about the WRs not being good.

83
by David B (not verified) :: Thu, 01/04/2007 - 10:19pm

Re 81:

Don't want to use DVOA for the same reason the As don't win the post season: having the most statistically succesful night doesn't mean you'll win (even in baseball). Ultimately, it's a game about winning, so what you want to know is if we've developed a statistical measure which tells us anything about why someone might win in the playoffs. For all we know, the eagles might go play the giants, dominate both sides of the ball for 3 quarters, rack up a 14 point lead, and then lose the game on a series of questionable calls and remarkable fumbles that fly forward to waiting Giants in the end zone.
The purpose of this excercise is to see if we can now identify which trends lead to playoff success...as defined by winning.

84
by Trogdor (not verified) :: Thu, 01/04/2007 - 10:25pm

Just a thought - how would the correlations change if some points were added for earning a bye? One team gets a bye and loses its first game, another doesn't and goes 1-1. Which has done better in the playoffs? Neither - they came equally close to winning the championship. Just thinking, tack on two points for a bye, run the numbers real quick, and see what happens.

85
by David B (not verified) :: Thu, 01/04/2007 - 10:29pm

On 84...it's a good thought, but it would skew the results by telling you who is more likely to get a bye, rather than who is more likely to win a playoff game. Since the rest of the results are about likelihood to win a playoff game, it won't look right (and will probably reduce both confidence and correlation).

86
by stan (not verified) :: Thu, 01/04/2007 - 10:29pm

76,

More on Colts' O-line -- did you watch them struggle in pass pro against the Giants in week one or the Pats? Pats should have had about a half dozen sacks that night.

87
by MRH (not verified) :: Thu, 01/04/2007 - 11:11pm

I had the same thought as trogdor. There are 5 possible outcomes for a playoff team:
Lose in rd 1 (wild card rd)
Lose in rd 2 (divisional rd)
Lose in conference championship
Loss in Super Bowl
Win in Super Bowl

I'm not sure the system of assigning playoff score points reflects these outcomes very well.

I tried this:
any loss = 0 pts
1st rd win = 1 pt
Bye = 1 pt (getting bye into 2d rd is same as winning 1st rd)
2nd rd win = 2
conf championship win = 3
Super Bowl win = 4

This translates to these pts per outcome:
Lose in rd 1 = 0 pts
Lose in rd 2 = 1 pt
Lose in conference championship = 3 pts
Loss in Super Bowl = 6 pts
Win in Super Bowl = 10 pts

From '97-'05, this gives the following correlation coefficients:
Total DVOA = 0.43
Off DVOA = 0.14
Def DVOA = -0.27
ST DVOA = 0.17
Wtd DVOA = 0.40
Non Adj VOA = 0.47
Est Wins = 0.48
Pyth Wins = 0.50
Actual Wins = 0.52

Defense appears to more strongly correlate with success than offense (it would be instructive to look at traditional stats to see how they correlate compared to DVOA).

Total DVOA looks much better - and still beats weighted DVOA. However, actual wins (among others) beats everything. I think this is because assigning one point to getting a bye biases the results - byes correlate completely with actual wins (and probably very strongly with Non-Adj VOA). Also HFA probably has a significant impact here, so the author's system of giving extra points for road wins might be better.

I didn't try to run the correlations for the various splits. What is clear to me though, is that the size of the correlation is affected by the system of assigning points. This system probably needs to be examined much more closely before proceeding further in assessing what predicts playoff success.

88
by MRH (not verified) :: Thu, 01/04/2007 - 11:29pm

HFA since NFL went to 12 team playoffs:

Rd 1: 43-21 0.672
Rd 2: 51-13 0.797
Conf Champ: 19-13 0.594

Teams with a bye (home in rd 2) do better at home than home teams with no bye (home in rd 1 and conf champ game). I think this is relatively well-known, but thought I'd put the numbers up (apologies for any errors in counting).

If the playoff point systme is going to reward road wins over home wins, is 3-2 the right ratio? Should it be larger? Should it vary by round? I think these questions need to be addressed by further research.

89
by bsr (not verified) :: Thu, 01/04/2007 - 11:50pm

#82 & #86 - They don't rank highly in power situations because they are built around a stretch play run scheme and are more light and quick then powerful. However, that doesn't mean they are barely adequate, even in run blocking. They rank highly in all other DVOA stats in both run blocking and pass blocking. They also have two probowlers on that line. Furthermore, the one traditional way to rattle Manning is with pressure up the middle. If the line was barely adequate, he would be rattled much more often then he is. There is no evidence to suggest that they are anything other a very good line. If anything, if the colts went to a more traditional power rushing line, you would then see a big decrease in pass protection.

As for the Pats and Giants games, both have good defensive lines. Especially the Pats who have pretty much manhandled every offensive line they have faced this year. It isn't fair to judge them based on one or two games where there could simply be bad matchups.

Rereading your post, I do see now that you weren't discrediting the WRs. My bad. I do have an answer for you about the cold effecting the passing game however. It isn't just the wind. The ball itself is much harder and heavier, which makes it more difficult handle and different to throw.

90
by mark cook (not verified) :: Thu, 01/04/2007 - 11:53pm

dudes, i love your stuff when i can read it. when you go all numbers and correlations on me i'm lost. suggestion: try to tease this information, which i'm sure would fascinate me if i paid attention in maths class, into somrthing resembling a narrative.

best, mark

91
by jbochow (not verified) :: Fri, 01/05/2007 - 12:01am

I really enjoyed reading this article. It is a good starting point for a deeper statistical analysis. Besides that it is also a good starting point to find what #75 called "causal mechanism" behind the data.
To me it seems that the reason why the "First Down Passing DVOA" and the "First Down DVOA" are so important is that these situation are likely to see the most variation in plays by the offense.
Therefore it is more difficult for the coaching stuff and the players to detect what the offense really wants to do with this play and stop them from doing so without guessing totally wrong.
A defense with a good "First Down DVOA"-value is a sign of team that has only few holes in its defense and has intelligent coaches/players. Generally if a defense can deal with complex situations like 1-10 it should also be able to deal with situation where the number of different plays they are facing is smaller.
A good "First Down Passing DVOA"-value indicates that a team doesn't get burned by a long pass. This enables the defense to stop the drive later on (to force a punt or only allow a field goal). It also helps at the end of the halves when teams often have to move the ball quickly (which leads to a passing play). If your defense has a higher prob of stopping this it gives you a vital egde in close games.

When looking at the chances of the two teams that rank best in the presented categories I would give the Patriots an edge over the Ravens in an actual game but I would give the Ravens an edge over the Patriots when it comes to playing the other teams.
To me the Bengals (before they decided that the play-offs would not matter to them this season) laid out the blue print of how to beat the Ravens: You have to have complex offense which keeps the Ravens defese guessing whats coming up because they have to defend a large field. You then have to move the ball without giving up turnovers on only 3 or 4 possesions. the most important point is to avoid that the Ravens get 10 points through their defense. If you can do that and still move the football for 13 or 17 points you have taken away the biggest asset of the Ravens. The Bengals did it as did the Patriots in a similar game against the Bears: Create a low scoring contest in which your offense is the bigger thread at the end of the two halves than your oponent one.

Looking at the Patriots their biggest weakness in my opinion is their lack of experience in the defense due to injuries. I prepared for the upcoming Patriots - Jets match by looking at previous two games this season. The Jets had the most success when they went no huddle thus limiting the influence of the coaching stuff and asking the defense if they could make the right reads on their own. In the first game the Patriots got the job done but in the second game they did not. In this game I believe they had more injuries in their defense and it made a difference under this circumstances.
I think, against the Patriots you have to have an experienced QB whom you trust to make his own decisions when it really matters. This would rule out the Chargers for me.

92
by Mr Shush (not verified) :: Fri, 01/05/2007 - 12:16am

On the question of why defense should be more important than offense in the playoffs relative to the regular season, I have a tentative suggestion. Coaches and players speak of a radical difference of approach going into playoff games. I submit that perhaps the most important way in which this manifests itself might be a change in the proportion of general to opponent-specific elements in training. That is, perhaps teams stop doing so much work on fundamentals or familiarity with the entire playbook, and look more closely at what is contained in this week's gameplan only. Let's call this premise 1.

We now need another premise: that it is in some sense easier or more effective to adjust one's gameplan for a specific opponent on defense than offense. This seems intuitively plausible. An offense will have six of the same highly specialised personnel (QB and OL) on the field for every single play, and they will be lining up in pretty much the same place. The defense has no such constraint, so more variations in personnel and alignment are possible. Moreover, the most important element of the defense - the pass defense - has to be geared primarily around the tendencies of only one opposing player - the quarterback - where an offense has to be adjusted to match up well against and be prepared for the tendencies of an entire unit.

So:
1. More emphasis is placed on gameplanning and game-specific practice for playoff games than for those in the regular season.
2. Additional game-specific emphasis improves defensive performance more than offensive performance (and the pure speculation element - this improvement is a multiplier-type effect, not the addition of a constant).

Therefore
3. Defense is more important than offense in the playoffs compared to the regular season.

Now, I'm not saying either 1 or 2 is true, but they do seem plausible to me, and if true they go some way towards explaining the facts.

93
by jonnyblazin (not verified) :: Fri, 01/05/2007 - 12:33am

"To me the Bengals (before they decided that the play-offs would not matter to them this season) laid out the blue print of how to beat the Ravens"

I'm not sure any of the playoff teams will be able to duplicate what the Bengals did that thursday night game for a couple of reasons.
First off, the Ravens didn't prepare for the game. They had 1/2 a practice on tuesday, and a walkthrough on wednesday. They stuck to the same gameplan they used during the first meeting, and the Bengals used 3 full practices that week to make adjustments to their original gameplan. Billick treated that week as a bye week (after the game the Ravens had off until the next wednesday), and it looks like it worked, because the Ravens played pretty well down the strech, whereas the Bengals folded like lawnchairs.
Secondly, the reason that the Bengals give the Ravens fits is because they have 3 legitmate deep threats and a great O-line which is familiar with the Ravens blitz packages. NE has 0 deep threats and an O-line that doesn't compare to Cincy's. Cincy can play ball control against the Ravens because the Ravens fear the deep pass, and thus play more conservative than normal.

94
by turbohappy (not verified) :: Fri, 01/05/2007 - 12:42am

Thanks MRH for looking at the points being used.

The points scheme HEAVILY punishes teams for doing well in the regular season (getting to the Super Bowl is worth 4 points if you have HFA, 9 points if you are a wild card team). Therefore, factors which contribute heavily to REGULAR SEASON success will be penalized under this system since teams with regular season success just don't have as many scoring opportunities.

95
by RF (not verified) :: Fri, 01/05/2007 - 1:01am

This thread might be the most enjoyable, enlightening conversation I've been involved with on Outsiders. Maybe it's because I have a casual interest in statistics and experimental methods. But the discussion being undertaking here, with statistically inclined people contributing ideas to the next step in this study, has been very interesting.

96
by chris clark (not verified) :: Fri, 01/05/2007 - 1:06am

:81/83 Pat, I'm surprised you made that mistake. Although, I think 83 said it better than I'm going to. The reason you don't use playoff DVOA as your dependent variable is that you are trying to measure playoff success, which is defined to be winning in the playoffs, not playing well in the playoffs. If you play better, but still lose, well, that wasn't successful.

So, the first part of the argument is whether DVOA correlates with playoff success, where playoff success is not measured by DVOA.

And, from a rhetorical point of view, it is important that the two measures be different, so that it doesn't appear one is trying to argue a tautology. An appearant tautology might be comparing SB wins to final record, since the final record includes the SB and playoff game outcomes, making it sound like the SB victory (loss) is part of both the dependent measurement and the independent measurement. Now, statistically, we can see that it isn't a real tautology, that the two numbers are not identical and not 100% correlated, but rhetorically it can seem like one (and one needs extra rhetoric to explain the distinction). Or in other words, until you have proven that DVOA correlates with playoff success, you cannot assume that DVOA (even playoff DVOA) correlates with playoff success--that's a falacy.

Now, once one has established that DVOA correlates (even weakly) with playoff success, then it is permissible to compare regular season DVOA with playoff DVOA to see if that more nuanced measure is well correlated. (Well, one can check the correlation without the supporting argument, it just isn't possible to draw the conclussion about playoff success without it.) So, given that one accepts the results of the article, then one can do the further measures you propose, and maybe get a stronger conclussion.

To bring this back to football, I'm curious how red zone defensive performance correlates with playoff success--the causal connection/argument. The reason being is that earlier in the season, Aaron called DEN's early red zone defensive success, unsustainable, which I didn't (don't) doubt, especially since it wasn't sustained. However, we now have contradictory evidence, that suggest that red zone defensive success is indicative of playoff success. Seems anomolous to me. Although, both statements can be true. This reader is suspicious.

97
by Eddo (not verified) :: Fri, 01/05/2007 - 1:15am

I strongly agree with RF (#95) that this has been one of the most enlightening threads I've ever read on the interweb.
I also can see where some people feel like bye weeks should get some points in the system being used by Bill. But ultimately, playoff success should be judged by winning playoff games, and having a first round bye is a result of winning regular season games.
Perhaps two separate analyses must be done. One could treat each playoff win as 1 point and each loss as 0. This would show some of the correlations between DVOA and simply winning games in the playoffs.
The second analysis could give different point values for reaching each round. This way, byes are included. This method would show some correlations between DVOA and likelihood of reaching certain success levels (conference champ, super bowl champ, etc.).

98
by David B (not verified) :: Fri, 01/05/2007 - 1:38am

Thanks MRH for rerunning it with a different score system - those results show that the score system is definitely impacting the level of correlation (more or less as predicted).

I still think that we're not going to be able to use a score system this skewed with the dataset we have right now. The value of a Super Bowl win is so large that we could essentially just do a dummy variable regression on all teams that played in super bowls for wins and losses (in other words...a win = 1, a loss = 0, and regress our various metrics). The reason for this is that total playoff score for a team is currently about double for the superbowl winner in either system, meaning that your high-end data values are so far removed from the next highest data point that whatever metrics are strongly correlated with the high scores will naturally pull up the rest. Our last 9 superbowl winning teams are thus having an incredibly strong pull on our dataset.

This is both good and bad. On the good side, we WANT to know who wins the super bowl, right? That's basically teh point of this analysis. On the bad side, with only 9 games we have to deal with the random and luck factors playing too big a role.

Examples from two super bowls:
Super Bowl 2005 (XL), Seahawks lose 21-10. Many of us thought at the time (sorry steelers fans) that this game could have gone the other way if not for bad officiating. Pit's def. DVOA (total) was -15.1%, Seahawks was -3.5%. While both sported rush DVOAs better than -17%, the seahwks were a terrible pass defense. If the officiating goes the other way, total defensive DVOA of the winner would impact our analysis by more than 100% less. This is because seattle got a score of 4 points (two home wins) while Pittsburgh won 3 road games and the super bowl.

Super Bowl 2003 (XXXVIII): NE beats CAR 32-29. New England wins after John Kasay kicks the ball OUT OF BOUNDS on a kickoff with a MINUTE REMAINING. The good field position allows Brady to set up a Viniateri field goal, which wins it. Now, while kickoff distance is very consistant, a kicker kicks the ball out of bounds so rarely on a kickoff in the NFL that this is most certainly a fluke. In 2003, NE had an amazing defense, with a total def. DVOA of -22% (rush dvoa of -10.9%). Carolina, on the other hand, had a defensive DVOA of -7% and a rush defense of -8.5%. In this case, Carolina won 1 home game and 2 road games, for a score of 8 while thats won 2 home games and the SB for a score of 9. While in this case the Pats win doesn't hugely skew things in favor of their amazing defense, imagine if Carolina had won. They would have had 13 points with a decidedly mediocre defense.

We need a better way to do these playoff score systems.

99
by jbochow (not verified) :: Fri, 01/05/2007 - 2:37am

#93
Points taken. The Patriots definitely don't have recievers as good as the Bengals. But they have a QB that reads the defensiv well which enables him to work well in a multi-reciever set. The Patriots tried this against the Vikings and another team (can't remember right now against which one). I don't think they only brought it up for playing against weaker teams in the regular seasons. It maybe won't work as well for them against the Ravens because their reciever don't have the quality but I wouldn't be too surprised seeing it if these to teams meet.
The lack of preparation time for the Ravens in the match against the Bengals was certainly a factor I forgot and this will definitely be different in an AFC championship game.

#98
I don't think that it's possible to overcome the problem of the relatively small sample size by adjusting the score system. But I think the idea of runnig the complete procedure with different score systems should give a hint how stable the different variables are. I' d find it very intersting to know.

100
by Andrew (not verified) :: Fri, 01/05/2007 - 2:48am

johnnyblazin #74:

The Ravens rank 2nd runs to mid/guard (3.78ypc) and 7th at right tackle (3.5ypc), but 1st at right end (1.99ypc). No area of the run D is weak, maybe a RB busted one long run off right tackle that skewed the average. I don’t think coach watching tape would think running at RT would seriously exploit the Ravens D.

When you look at the numbers, middle/guard and right tackle are the most attractive areas to run at against the Ravens. Tatum Bell was able to find some nice creases there for 10+ yard gains, and also off left tackle. The right O-Line, one big enough or with the right technique to manhandle the Ravens D-line and linebackers, can make those creases.

I think the problem with trying to attack Rolle downfield, where he’s been burned several times this season, is that then the QB has to sit in the pocket for a while , and if that reciever is doubled or not open, the QB will likely be crushed by Suggs, Scott, etc.

Not if those guys are busy having to watch for Tight Ends and Running Backs in the flat and seams. A team with multiple receiving options, and that can run out of a pass formation or pass out of a run formation, can make problems here by causing too many leigitmate options to need coverage. Colts, Eagles, and Patriots all look dangerous with that in mind. Imagine the Patriots, for example, come out with one wideout, Watson and Graham as Tight Ends, and Evans and Maroney in the backfield. Looks like a run, right? But if the Ravens substitute to a heavy defense, Brady can motion guys out who become big coverage liabilities to slow linebackers and small safeties. OTOH, if they stick closer to a base defense, all the big offensive guys should be able to bully holes open for Maroney.

A team would need a real burner as a #2 reciever (assuming McCalister covers their best WR) to cause problems, the only team that really has that is the Colts.

In the NFC, the Eagles, Bears, Cowboys, Seahawks, and Saints all have #2's good enough to exploit him.

Of course, if the Ravens cover a team's best reciever with Rolle (see Lee Evans TD), then they are screwed.

Don't the Ravens cover by side of field, like almost everyone else in the league, and not by placing a CB on a specific WR?

101
by Pat on the Back (not verified) :: Fri, 01/05/2007 - 3:18am

My 2 cents:

Cent 1: Even if we could get DVOA stats from back in the early 90s, I think you could make a pretty decent argument that the results would be meaningless, as the institution of free agency (and teams coming to grips with how to play the cap after grandfathered contracts disappeared) probably means there is no stationarity of the variances. Teams in the early 90s could have a great O, a great D, and great depth for both. Now, it is sort of a pick and choose combo of great frontline starters/no backups or depth with no real stars. You won't get consistent results much before 97 anyhow.

Cent 2: I think we probably do have some heteroskedasticy with the "high point" teams, though I'd bet our lower point estimations would be pretty robust. I'd be curious to see if Goldfeld-Quant test was significant or a partitioned point barrier would significantly change our estimates for high and low. Certainly I do think there are two pretty different populations, with the "high point" teams probably being under-represented. With our data, we probably can't figure out what leads to playoff wins, but we can probably get a pretty good idea what leads to playoff losses.

Bonus cent: there also is probably some screwiness in the data that comes from good teams hitting good teams and poor teams doing the same. The recent strength of the AFC playoff field, and weakness of the NFC, may also be playing hell with the high-point group. The AFC has been the stronger conference since 2003, if not earlier. That is 40% of the data set.

102
by Andrew (not verified) :: Fri, 01/05/2007 - 3:36am

MRH:

You seem to have an extra win counted in the Championship round. The actual tallies are 18-14 since 1990. Both home teams won in 1991, 1993, 1995, and 1996, while both lost in 1992 and 1997. They split in 1990 and every year since 1998 (hmmm ...).

The data also appears to be shifting since the divisional realignment in 2002, which also shifted the playoff format (#4 seed is now 4th divisional winnner, instead of the 1st wild card). The divisional realignment has made the #5 and #6 seeds much more competitive than they were before in the first round only.

HFA
1990-2001
Wild 73% (35-13)
Div 81% (39-9)
Cham 58% (14-10)

HFA
2002-2005
Wild 50% (8-8)
Div 75% (12-4)
Cham 50% (4-4)

Part of this is that teams that would have been #4 seeds in the pre 2002 format would be #5 seeds today, so the formats are not really comparable. For example, 97 Broncos, 99 Titans, and 2000 Ravens all would have been #5 seeds and on the road, instead of #4 seeds at home, while the 03 Titans and 05 Jaguars would both have been #4's at home instead of #5's on the road under the old format.

From 1990 to 2001, in only two years, 1992 and 1997, did home teams not win 7 or 8 games. Since 2002, home teams have won 8, 6, 6, and 4 games. If I had to guess this year, I'd say 1 or 2 home teams fall in the wild card, 2 or 1 in the divisional based on whether 1 or 2 win the wild card, and 1 falls in the championship round.

Some other trends to watch:

It used to be that the AFC's #3 (14-2) and 4 (11-5) and the NFC's #4 (11-5) seeds almost always won in the wild card, while in the NFC, the #3 seed was almost comically bad at defeating the #6 seed (#3's are 7-9 since 1990). These trends have not been as solid since the 2002 realignment.

The NFC's #1 seed has never missed the conference championship game since 1990, going 16-0 in the divisional round, while the NFC's #2 seed is 12-4 in the divisionals. In the AFC, OTOH, the #1 seed has frequently choked, going 10-6 in the divisionals while the AFC #2 seed has gone 13-3 in the divisional round. If any team with a bye should be nervous based on history, its San Diego. OTOH, the Bears should be supremely confident.

Only 3 #3's and 1 #5 in the NFC have made the Championship round, and just 1 advanced to the Super Bowl. In the AFC, OTOH, 2 #3's, 4 #4's, 2 #5's and 1 #6 have made it, and 5 of those 9 went on to the Super Bowl.

In the NFC 10 of 16 #1's have gone to the Super Bowl, along with 5 #2's and 1 #3. In the AFC, 6 of 16 #1's have gone to the Super Bowl, along with 5 #2's, 4 #4's, and 1 #6. If something crazy is going to happen with the top seeds missing the Super Bowl, its probably going to be in the AFC, where it occurs about 1/3 of the time.

103
by David B (not verified) :: Fri, 01/05/2007 - 3:42am

Before I beat the score system to death one more time, I want to put out a different kind of model for discussion.

I'm thinking though that a more constructive model would be a model which gives ua percent likelihood of winning a playoff game against an opponent with any given DVOA. In other words, we take every playoff game that was played on a head to head basis and look at the differences in DVOA between the two teams, and then regress. This might take care of our opponent adjustment. We could even add in a dummy variable for home field advantage to the regression, and we could also add in that team's DVOA variance. In other words, a given teams likelihood of winning is equal to it's difference in DVOA in X (where X is total, run defense, pass offense, whatever) compared to its opponent, multiplied against some Beta test statistic, +/- some Beta for home field advantage. Then we can add variance to the result to get a likelihood of winning estimate.

(Skip if uninterested in stats. The dependent variable will be 0/1 for loss/win, meaning that our beta estimator will be some sort of scalar to multiply against the DVOA difference. We can then quantify how statistically significant this scalar is. In this case, a multivariate analysis would be appropriate, dropping variables with insignificant t-statistics until only significant variables remain. Remember, correlation coefficients will alwayas be VERY small when all we have is half of the game to study. Would you really expect a team's defense, regardless of it's offense, to be more than 50% correlated with victories?)

As for the score system (and Bill's existing model)...I'm still interested in doing this with just 1s or 0s for wins/losses. It still gives the super bowl winner the chance for influencing the statistics more (one more game of a win), but it's more fair in that it just tells us which aspects of a football team are conducive to earning playoff wins. Essentially, I'm arguing that EVERY playoff win is the same as any other, and that some sort of unkown exogenous factors may determine who wins or loses the super bowl so we shouldn't get too caught up in trying to predict the super bowl winner. Rather, we should just try to predict what creates the most playoff wins.

I'd love to do some of this work myself but I haven't got the time at the moment. Anyone want to do it?

104
by David B (not verified) :: Fri, 01/05/2007 - 4:27am

One other thing from the previous post that I forgot to mention (sorry for double post): The relative size of our scalars tells us their importance in terms of predictive power. Imagine, for instance, that we have a formula that looks like this: WIN\LOSS = B1*(delDVOA Defense) + B2*(delDVOA Offense) + B3(delDVOA ST) +B4(Home/Away) + Error (del => difference between home team/away team) If B1 = 20, B2 = 10, and B3 = 5, then for any given pair of teams a 1% increase in the difference of defensive DVOA is 2X as likely to lead to a playoff win (for the higher team) than a 1% incresae in offensive DVOA, and 4X as likely as a 1% increase in special teams DVOA. Does this make sense?

(about the win\loss...when we run the regression, it'll be a 1 or 0. When we want to make qualitative conclusions about future success, we'll plug in the current team's differences and see what the formula results in. A result of 1 would indicate that the formula believes there is a 100%, +/- error term, that the given team will win.)

(ps...these numbers are completely hypothetical and for demonstration purposes only. I do not think that the real estimators would be that large, or necessarily in those proportions.)

105
by Bill Barnwell (not verified) :: Fri, 01/05/2007 - 4:45am

Hey - me again. I agree the discussion has been really interesting and I appreciate everyone's kind words and the criticisms have been really intelligent.

When it comes to the Playoff Score Points, to be honest, I think they can be improved. I spent about 30 seconds figuring out what to make it. My initial thought was to do it that way and ignore the byes specifically because we would then be rewarding teams further for regular season performance and that would be counterproductive.

106
by Lobolafcadio (not verified) :: Fri, 01/05/2007 - 6:15am

Anyway a great article to read. Sometimes, common sense is right.

Do you think BB employs stats guys to be aware of this kind of things ?

107
by Yaguar (not verified) :: Fri, 01/05/2007 - 6:45am

Bill, I just wanted to tell you I think this is by leaps and bounds your best article this year, and one of the best I've read on FO this year.

108
by Pat on the Back (not verified) :: Fri, 01/05/2007 - 10:25am

Another thought on playoff weighting:
Rather than try to assign the differing weights and figure out how to handle the bye, you could set up a regression equation for each round of the playoffs (wild card, division, conference, superbowl) and see which statistics matter at each level. While the sample size problem would be compounded for the SB (And somewhat for the conference games), we could see if the 4 equations would be better with either a restricted or 3SLS estimation model. This also would accomplish the "weighting better teams heavier" just by their presence in multiple data sets, but also benefit the teams that had enough regular season success to skip the wild card. The bye teams aren't hit with a penalty, and teams that win get deeper into the data and have more representation later.

It would be interesting to see if the estimated coefficients move much from round to round (i.e. what forecasts winning in the WC round is different than in the super bowl).

109
by Wanker79 (not verified) :: Fri, 01/05/2007 - 11:16am

I just posted this in the DVOA thread, but it seems just as relative here and I spent/wasted (depending on your point of view) too much time putting these together not to post it all over.

I put together graphs (yes, they're xls, eat me Pat) for all the splits. I only have the playoff teams labeled. Offense and Defense for a particular split are on the same graph.

I haven't really looked at them very closely yet, but the one thing I can say with confidence is that if anyone passes in the red zone on San Diego, whoever is calling the plays should lose their job.

Enjoy.

110
by Savage Towel (not verified) :: Fri, 01/05/2007 - 11:16am

I think it's important to point out, not that good kickers are irrelevant in the playoffs, but that kickers performance during the season has little to do with their performance in the playoffs. This seems like nitpicking, but it doens't necessarily disprove the notion held by some that there are certain clutch kickers out there that switch on for the playoffs, like Vinatieri. Personally, I'm more of a 'if Tony Womack can go four for four two days in a row, vinatieri can make a small number of important hard field goals without it being indicative of anything' school of thought.

111
by Jimbo (not verified) :: Fri, 01/05/2007 - 12:49pm

Re: 102

This is a great post. I don't feel like there's been enough appreciation for the post-season impact of the 2002 re-alignment. The old #4 seed (best non-division winning team) was often very, very good (97 Broncos, 99 Titans, and 2000 Ravens). Now that role is played by the #5 seed, and you can end up with some weak #4 seeds and some very strong #5 seeds.

112
by Sam H (not verified) :: Fri, 01/05/2007 - 1:52pm

This is another interesting article from you guys. However, let me just suggest that this series of bivariate correlations can be highly misleading. For instance, take the finding that offense in general is almost unrelated to playoff performance. Now think about that for a second. Do you really believe that two teams identical in all other aspects, one of whom had the offense of the current Colts and one of whome had the offense of the current Bears, would have similar expectations in the playoffs? It doesn't take much to realize that this is not a reasonable proposition. Perhaps the issue with the data is that high-powered offenses are correlated to some degree with characteristics that hurt team performance, like below average defenses. In any case, these kinds of bivariate associations should be taken with a few shakers full of salt, and conclusions like "A good offense doesn't mean very much" should be avoided without a lot more analysis. You guys do great work, but I think this is an instance of really overstepping the bounds of what the data can reasonably allow us to infer here.

113
by Pat (not verified) :: Fri, 01/05/2007 - 2:03pm

Bit of a response, but also a response to "why should this be so?"

The reason you don’t use playoff DVOA as your dependent variable is that you are trying to measure playoff success, which is defined to be winning in the playoffs, not playing well in the playoffs. If you play better, but still lose, well, that wasn’t successful.

A high VOA in a game is correlated with winning it. You're not looking for a change in the game in the playoffs. That's where you wouldn't want to use VOA from the game, rather than wins/losses, because you'd be looking for "situations where teams win games more often than their VOA for that game would imply."

Now, once one has established that DVOA correlates (even weakly) with playoff success,

You don't need that. You just need to show that VOA in a game is correlated with the chance of winning a game (which it is). The rules of the game don't change in the playoffs (not converting a 3rd down is still bad), and so using VOA as a better evaluator of the game than just a "1" or a "0" should still be fine.

The assumption that the rules of the game don't change in the playoffs could be tested, of course, but I don't think it's an assumption that really needs serious testing.

It's not really a tautology. You're just subbing out "win/loss" as a measure of performance for "VOA" as an attempt to gain more information.

You're just using VOA rather than wins/losses to compensate for situations where, say, a good team faces a good team early. Yes, a loss is a loss, but it's reasonable to believe that if, say, Indianapolis barely loses to the eventual Super Bowl winner in the first playoff game they have, that had they taken a different path, they would've had more postseason success (though eventually lost to the Super Bowl winner later). It's less reasonable to believe that if Indianapolis gets pounded in the first playoff game (see the Jacksonville Jaguars, New York Giants in 2005).

What you're looking for are classes of teams that can best handle the kinds of teams seen in the playoffs. Think of it this way: the regular season is a filter which selects out certain teams for the playoffs. Typically, those teams have great offenses (like, say, the Colts) because offense wins football games against the average team.

Once you get into the playoffs, though, you're no longer facing average teams. You're facing playoff teams. So the question isn't "what wins games against average teams?", it's "what wins games against playoff teams?" And I don't think it's surprising that the answer is "defense".

In short, to respond to #30: "why is this so?"

Because in the playoffs everyone has a good offense (on average). Otherwise you wouldn't've gotten there. Not everyone has a good defense, though - and those teams are the ones who win.

114
by Pat on the back (not verified) :: Fri, 01/05/2007 - 3:17pm

Feeding off post #112, another possible reason for the lower correlation between success and offense than on the defensive side is that there might in fact be some endogeneity between offense and losing. Teams that are really good at offense often times do so because they are forced to attack harder (and against prevent defenses) because they are down or in a close game. While DVOA tries to control for this, I think you could make the argument that a team with a weaker defense in some ways makes the offensive numbers (both counting stats and likely some part of DVOA) go up. So it might be that the stats above are picking up the fact that inferior teams are down a lot and are trying to get back in the game, and do so better than the usual dreck that gets steamrolled in the regular season (thus higher DVOA offense in the playoffs, but getting the loss).

Basically, a good offense with a poor defense will probably generate a better DVOA than the same offense with a better defensive/ST compliment

I realize that I'm kind of rehashing my original argument over this site's first ever piece (that teams that are down in the score and abandon the run probably contribute to their blowout by making it easier on the defense; lack of rushing when down is a poor strategic decision that compounds the deficit more than the advantage of saving time on the clock), but hey, can't blame a guy for trying.

115
by Bobman (not verified) :: Fri, 01/05/2007 - 4:02pm

Wanker79, nice graphs, if slow to load. Interesting to note that Indy's D is roughly average for playoff teams on 2nd down. Terrible on 3rd downs. Hmm, so they key is to keep the opponent out of 3rd down situations.

116
by Pat (not verified) :: Fri, 01/05/2007 - 4:28pm

Feeding off post #112, another possible reason for the lower correlation between success and offense than on the defensive side is that there might in fact be some endogeneity between offense and losing.

Except the correlation isn't "DVOA in the playoffs" to "playoff success" - it's "DVOA in the regular season" to "playoff success" - if offense in the regular season were boosted by losing, teams in the playoffs would have a lower than average offense than you would expect (since they won).

I think the lack of correlation of offense is probably correct, but there's a bit of 'hidden assumptions' present here, so #112's strawman doesn't really apply.

The argument there was "suppose Team A has the Colt offense, and Team B has the Bears offense. They are otherwise identical. This implies that the playoff score points for the two teams will be roughly the same. This is clearly crazy."

My response is - no, it isn't. Why? Let's use the Ravens, rather than the Bears, because the Bears are bipolar weird. The Ravens offense is just "meh" (over the whole season).

Suppose Team A has the Colt offense, and the Colt defense. Now Team B has the Ravens offense, and the Colt defense. Will they go the same distance in the playoffs? No. Because Team B will never get to the playoffs in the first place.

Now suppose Team A has the Colt offense, and the Ravens defense. Team B has the Ravens offense, and the Ravens defense. Will they go the same distance in the playoffs? In an average year, more or less. Team A would be a prohibitive favorite to win the Super Bowl. But Team B would as well - or at least, to go deep into the playoffs. There's no bonus points for demolishing opponents on the way to a Super Bowl victory here.

In fact, Team B might score roughly as many playoff score points without even getting to the Super Bowl. With a lesser offense, they'd be more likely to be a lower seed, and need to play four games. A home win, road win, road win is 8 points. A home win, home win, Super Bowl is 9 points.

I think the important thing to realize is that the baseline for teams in this article is they must be in the playoffs. This means that they can't be the Raiders, and that they're going to have a non-awful offense already.

117
by Pat (not verified) :: Fri, 01/05/2007 - 4:40pm

Actually, let me put a little request out for Bill here:

Bill, can you calculate the average offensive, defensive, special teams DVOA for playoff teams used in the study? Correlations say "increasing X increases Y" - but the baselines for playoff teams are no longer 0% offense, 0% defense, 0% special teams, so we don't know what "good" and "bad" are.

For this year, for instance, it's:

Avg. Offense: 9.42%
Avg. Defense: -2.78%
Avg. Special: 1.65%

Last year it was much more balanced (there were a lot of balanced teams and meh offenses last year), but in 2004 and 2003 it was similarly split.

118
by princeton73 (not verified) :: Fri, 01/05/2007 - 5:00pm

another way to ask some of the questions embedded in #113 is

"what components of regular season DVOA are most likely (or least likely) to be maintained in the postseason"

119
by chris clark (not verified) :: Fri, 01/05/2007 - 5:56pm

:113 Actually, it hasn't been established that VOA in the playoffs correlates to winning in the playoffs. Now, I'm not seriously suggesting that it doesn't and the rhetoric that the game hasn't changed between the regular season and the playoffs make it a reasonable hypothesis, but it is only a hypothesis until it is proven (and I'll even allow a lower standard of proof given the reasonableness of the hypothesis).

On the other hand, as you state later, one isn't playing average teams (and thus, not average games), therefore the metric for a playoff victory might be different, and VOA might not be the correct one (although I'd be surprised if it were far off), since it was based upon regular season comparisons. (see below)

We have the same issue with BB's PSP metric. We don't know that it is correlated with post-season success (except as it is defined by the metric), and their is already evidence that it penalizes teams that get a first round-bye rather than winning a wild card game.

However, I like the article, and we are in a position to use his hypotheses and test them. Barring unforseen circumstances, some team will win the SB this year, and that team will have various DVOA (and other) stats/metrics. They will even confirm the current correlations or modify them and there are statistical tests to verify whether the correlations were confirmed or not. We can repeat this experiment each year until we have sufficient confidence in the correlations.

below: I already asked one question about the difference in regular season and playoff correlations. Aaron hinted that red zone performance might be an unsustainable stat during the regular season. Howewever, regular season red zone performance is an indicator of PSP, as BB defined it. That leads one to the question, as to what's different between prior red zone performance predicting later regular season games and predicting post season games? Answer that and you may have some insight into what it takes to win in the playoffs. Or you may find a small sample size artifact or an artifact caused by the definition of PSP or some other factor. But, if it teaches us something about football, then the site has performed its purpose in my eyes.

BTW, I'm interested in red zone performance, because I think it might be a contributor to what I call measurable "luck". I think that the number of times a team gets into the red zone but doesn't score or keeps the opponent from scoring in the red zone, especially in "close" games might be one good metric of lucky teams, and a way to further refine the STOMP system. A skate without any opponent red zone visits that led to scores (or led only to FGs), might not actually be as close as a skate where the opponent reached the red zone, but the team got "lucky" and the opponent didn't successfully score (or got a FG rather than a TD).

120
by Chubby D (not verified) :: Fri, 01/05/2007 - 6:08pm

Hey guys, great article, and some of the most intelligent opinions and ideas coming from it. I have a couple things I would like to add:

On the scoring system, to beat a dead horse, I would try and correlate to pythagorean record. Scoring and preventing points are the keystones of winning not just in football, but all sports. This would prevent the large swings in leverage given to a team that went on the road to win every game and the Super Bowl over a team that played at home twice and lost to said team. I have a hard time allowing a difference of this magnitude for teams that made it to the same point, one winning and one losing. In addition, albeit again from a small sample size, it allows for the projection of how a given team would do under the "playoff microscope" for long periods of time.

Now, as for the point of kicking, I have done an exhaustive study on when a team should punt, kick, or go for it. I won't go into the details (I once wrote about five pages on it, and it has been beaten to death on this, and many other websites) but it basically generated three graphs from 1 (your own 1) to 99 (your opponents 1) showing how many points a punt (i.e. how many points are being "taken away" from the opponent), a field goal, and a GFI (go for it) are worth, less the opponents expected point given a failure. The main point that I saw was that field goals are highly overrated. It pointed out that in most cases, going for a first down in enemy territory is the right thing to do. The major caveat is, of course, the lack of time/score situations. Even with fouth and inches from the opponents 5, if you're down by two with one second to go, you're gonna kick!

Great job guys!

121
by Pat (not verified) :: Fri, 01/05/2007 - 6:53pm

since it was based upon regular season comparisons.

It was based on average comparisons. That is, what's the "average" performance of a team, where "average" is a multi-season average.

The only thing that changes from regular season to postseason is the quality of the opponent. The assumption that VOA still remains a better measure of a team's performance in a game than the score (or wins/losses, same thing) is the same thing as saying "VOA can be adjusted by opponent strength."

Let me put it another way - you could also just use the log5 winning percentage from points scored/points allowed, or the output of any of the game-output functions used in stuff like Massey's rating. All you're really trying to do is say "if a team in the playoffs beats another team 21-10, how many times would they win if they played them 100 times, same turf?" - and I think making the assumption that that relation doesn't change in the playoffs is probably pretty safe.

In any case, though, any problems that would show up in that case would show up in the regular season as well. Philly did play New York just a few weeks ago.

So using VOA in the playoffs as a substitute for performance is really the equivalent of saying "We believe opponent adjustments work." I think that's a safe assumption (at least, it's a consistent assumption).

122
by Bill Barnwell (not verified) :: Fri, 01/05/2007 - 11:53pm

Just a quick note guys -- I've made my way through this thread a couple of times but I'm sure I lost some of it and it will be buried by the time I get back.

If anyone has any specific questions or requests for me, please send them via e-mail to bbarnwell *AT* footballoutsiders.com. I'll answer them as soon as I get back.

123
by Rusty Jay (not verified) :: Sat, 01/06/2007 - 2:17am

A lay person's thoughts: Ya'll have touched on this point but missed something esssential. Success in the playoffs isn't about winning the most games-it is about not losing. Hence, the first round bye is the most effective way to get to the second round(it never fails.) A wild card team that wins the SB is no more successful than the team that wins the SB using a first round bye.

Or maybe I'm missing something.

124
by Rusty Jay (not verified) :: Sat, 01/06/2007 - 2:26am

Lay person again.

The whole concept of granting additional points for winning on the road seems flawed. Home field advantage doesn't materialize in some mystical way separate from the offensive and defensive statistics. HFA impacts the statistics themselves. The team with the best stats wins-invariably if we look at all of the stats. So giving additional points for road wins skews the stats from that game by giving them additional unearned value.

125
by Starshatterer (not verified) :: Sat, 01/06/2007 - 3:11am

Rusty Jay (#124 )--

The reason you award more points for road wins, and no points for a first-round bye, is the same: you trying to find factors that grant playoff success, that are different from other factors that grant success in the regular season. Bye weeks and home-field advantage, are known factors that make for success, and they work in the regular season.

126
by Bright Blue Shorts (not verified) :: Sat, 01/06/2007 - 10:29am

I guess it's no surprise that the kicking game is the least important predictor of success in the playoffs. Think how many blowouts there are in these games. On those occasions the Offense and Defense were much more important.

The trouble is that on a few occasions (e.g. Jim O'Brien, Scott Norwood, Adam Vinatieri) the game does appear to come down to the kicker.

However the savvy coach knows there were 59+ minutes before that time for his offense or defense to have won the game and therefore to have avoided the pressure kick.

BBS :)

127
by Eddo (not verified) :: Sat, 01/06/2007 - 1:36pm

It seems like the biggest question mark regarding this study is how to quantify playoff success. Is it measured by (a) outplaying your opponent, (b) winning games, or (c) advancing as far as possible?
If it's (a), determining correlation between regular season DVOA and playoff DVOA should be enough. If it is (b), each playoff win should count the same. And if it is (c), you could assign a point level to each round that a team reaches (e.g. WC=1, DR=2, CC=3, SB=4, SB Champ=5).
However, finding a way everyone agrees on is probably not going to happen. Maybe someone with a better knowledge of statistics that myself could crunch these numbers (or maybe I'll take it upon myself to learn how to calculate correlations and such).

128
by Joshua (not verified) :: Sat, 01/06/2007 - 4:29pm

Bill, phenomenal work. This is one of the best FO articles--this year or any year. The coments as well are phenomenal.

129
by chris clark (not verified) :: Sun, 01/07/2007 - 4:32pm

If I read the analysis right, we have already found at least factor in playoff success that correlates significantly differently than it does in tne regular season, red zone defense. Not that red zone defense is not important in the regular season, it is, but that it isn't predicitve of future games success, that it is unsustainable, or so I have read. To me that, if that is true, it is an important result, it says something. Perhaps red zone defense is dramatically affected by luck over short stretches, but over a season that luck tends to average out and a true measure of red zone defense is possible.

And, this goes back to some of the other comments, the playoffs are different than the regular season, if for no other reason than they are loss = out. That goes to the whole premise of the article. Can we determine stats that are usable to predict playoff success?

And, that was my whole nit with Pat, that one cannot assume that the normal season stats are meaningful for playoff success until one has proven it. The fact that it is reasonable is not sufficient. If I look out my window, the world looks relatively flat, thus a reasonable suggestion is that the earth is flat and I bet not one of you would not say that you do not know which direction is down, thus with an assumption that down is a true direction, we have a proof of a flat earth, but that hypothesis doesn't hold up to *all* the evidence, because my local down isn't actually your local down. Therefore, one has to be real careful with ones assumptions, as they can drastically change the results. Note, I think Bill has gone a long way to establishing that playoff sucess can be measured and stats do apply, and given that I think one can then accept Pat's argument that VOA or DVOA or any of the other related stats can then be analyzed to give us a better feel for how teams do.

Still, with the loss = out nature, one must realize that the statistical base is much smaller and that certain "luck" factors play an even more dominant role in determines who advances. It is harder to know how the teams who lost 1 game might have fared if the match ups (i.e. which team played which) were different, because in 1-and-done tournaments, those games are never played. Moreover, we are starting with a small data set to begin with, 11 games in an entire post season, approximately 1 weeks worth of games. And, because the winners play winners, some teams are represented more than once.

These factors compound the statistical issues. As a result, it would not be surprising to learn that choice of "playoff success metric" (i.e. how we assign values to wins and losses of the various games) might be very important in which features correlate with success.

One good thing is that factors which are truly significant in success should show up in many different metrics. Thus, redoing the analysis with different metrics and still seeing some factors as important, helps assure one that one has measured the right factors.

This brings me full circle. The initial results suggests that red zone defense is significant. However, it is possible that that result is an artifact of the small data set and that for a few key teams, it was one of their statistics. Further analysis may confirm or debunk that hypothesis.

Fortunately, I would expect with the stats here on FO, this question can be investigated. And, since it fuels some common "knowledge/myths" like whether bend-but-don't-break defenses work or not, I figure someone will.

And, here is a point where using VOA (or DVOA) can add insight. If red zone defense is not predictive of future red zone defense in regular season games, but it is predictive of red zome performance in plaoff games, that tells us one thing. If it isn't predictive in playoff games (i.e. in the VOA stats of those games), but it is predictive of playoff W/L reocrds, the tells us something else. Finally, if it isn't predictive of either, but is predictive of SB winner (or some other measurement), that tells us still a third thing.

In other words, we don't just assume that the results we knew from the regular season carry over into the playoffs, we test that hypothesis. And, where the results are confirmed, we have evidence that the same factors are at work. And, where the results are contradicted, we can do more to determine what the contradiction is telling us.

130
by Darrel Michaud (not verified) :: Sun, 01/07/2007 - 6:54pm

This is a LONG thread and I just wanted to stick this in here if it hasn't been said already - perhaps we can increase the sample size by looking at regular season games in which two playoff teams played?

131
by doktarr (not verified) :: Sun, 01/07/2007 - 9:07pm

Frankly, while all of this is interesting, I think that all conclusions are HIGHLY suspect and that we are simply a victim of sample size.

The Pats, Bucs, Ravens, and Steelers were all primarily defensive teams, and they all won in the DVOA era. If we expanded our analysis to include, say, the 1993-1997 postseasons (when more offensive-oriented teams won the Superbowl), we would get very different results.

Once again, correlation does not imply causation.

132
by Pat (not verified) :: Sun, 01/07/2007 - 11:19pm

1993-1996. 1997 is included. And it's not like Denver (in 1997) had a bad defense. They had a top-10 defense as well.

133
by Pat (not verified) :: Sun, 01/07/2007 - 11:26pm

And, that was my whole nit with Pat, that one cannot assume that the normal season stats are meaningful for playoff success until one has proven it.

I really don't think you're understanding what I'm saying. VOA is a stat that is purely in-game. It has very little connection to the actual regular-season stats (DVOA, by contrast, does, which is why I wasn't suggesting DVOA) - it has some connection to "average previous seasons" but that washes things out pretty well.

If you really wanted to, skip VOA, and instead of using VOA, use the average log5 "points for/points against" percentage of all games the team faced in the playoffs. All I'm saying is that treating a 23-20 win the same as a 37-17 win is a little silly. A team that demolishes its way through the playoffs should rate higher than one that squeaks through.

134
by sippican (not verified) :: Mon, 01/08/2007 - 1:15am

The article was fun and interesting to read and the comments were as well.

I have nothing to add, except "jive" is indeed wrong, "jibe" is not incorrect but not preferred. It's gibe.

Gibe is 27% more correct than jibe, or correcter, as we say in the nitpicking business. It's way correcter, really. Correctopia, almost.

The 27% ratio is of course weighted by WNOA, Webster's Adjusted Nitpick Over Average. The average is determined by comparing the subject word, phrase, swear, or meld of Brady and Manning's name into one word, to a carefully crafted list of misspelled words, including the word mispelled. Others include:

-Hipocracy
-Evar
-To
-Not that "to," the other "too." No, not that one. The other other one.
-Packyderm
-Arguement
-Dinning Room

and many others only known to our secret cadre.

You may now return to trying to figure out how the Colts are going to hold the ball for the 49.5 minutes a game necessary to keep their defense off the field at all costs, even if they score in ten seconds every time; and if punting on first down on offense and having Devin Hester score all your points will work for the Bears.

135
by chris clark (not verified) :: Mon, 01/08/2007 - 1:27am

:133, And I don't think you understand what I'm saying. It wouldn't help me to substitute any other measurement, because I don't know how those measurements are related to the desired result.

Treating a 37-17 win as different than a 23-20 win for purposes of predicting *another* game's outcome is unfounded, until you've established the basis for it.

Now, that Bill has established that there are statistical correlations, one can take it farther. But, without that basis, doing VOA or any other analysis is "assuming the conclussion" and invalid reasoning. It may be silly to you that you can't make that assumption, but it is an assumption until you've proven a basis for making it.

Do you really know that teams that win playoff games by high margins are more likely to win the SB? I don't know if that's the case or not. It seems likely, but I don't know if it is true. Maybe winning a blowout game uses up all a teams emotional energy and they play the next game flat and lose.

Without evidence, I'm not sure that I would count the rout SB's that the 49ers had against the AFC as more indicative of how to win a SB than the close games won in defensive struggles, say by the Titans and Ravens. And that's my point, I don't know that a 37-17 SB win is more significant than a 23-20 SB win, in terms of predicting how some other team might do in the SB.

Show me the basis first, then I'll believe your arguments. Bill has shown us his basis. I believe him.

136
by Ralph (not verified) :: Mon, 01/08/2007 - 1:51am

The New England Patriots won their 3 Super Bowls by a FG each and you are seriously trying to say losing Vinatieri isn't a big deal.

Please.

137
by sippican (not verified) :: Mon, 01/08/2007 - 3:04am

So I'm watching the Pats game today and observing the kickoffs sailing out of the endzone instead of landing on the seven, and watching Gusto pound 13 points through the uprights in a playoff game, and I'm wondering if anybody but me notices it.

Guess so.

The Pats won by three points in those games. I don't recall the score being 3-0 though. I think some other things happened. Touchdowns and whatnot.

Besides, as we have learned by watching the Cowboys/Seahawks game, Ken Walter was the most valuable player on those Pats teams.

LACES OUT!

138
by Bill Barnwell :: Mon, 01/08/2007 - 3:36am

Come on Ralph.

Vinatieri played a massive role in the Pats-Raiders game in '02, when he kicked the two field goals in the snow.

In that Super Bowl? He hit a game-winner on turf. Was it a clutch kick? Sure.

Two years later, Vinatieri's game-winner was only necessary because he missed a 31 yarder earlier in the game.

Finally, in the third championship, Vinatieri's output consisted of a 22 yard field goal. Anyone short Lawrence Tynes would be hard-pressed to miss that.

139
by doktarr (not verified) :: Mon, 01/08/2007 - 4:48am

RE: Pat #132,

I was referring to the 1997 postseason, like I said, which was not included. I don't have hard data to back this up, but my suspicion is that the six champs immediately before the DVOA era (Redskins, Cowboys, Cowboys, 'Niners, Cowboys, Packers) were all more offensively oriented clubs. And I don't think they were the exceptions in those years (those 49er teams that lost to the Cowboys in the championship game were high-offense clubs).

This is not intended as a knock on Bill, who did a solid analysis given a tiny data set. I just think that it's a statistical fluke caused by small sample size. Our much more robust data from the regular season suggests that offense and defense are roughly equally useful, and nothin here convinces me that the same would not be true in the playoffs.

140
by doktarr (not verified) :: Mon, 01/08/2007 - 5:15am

Let's look at this from a very simplistic perspective. I'll just look at the two teams in the super bowl, and their offensive and defensive rankings in regular season points scored and allowed, from 1991 to 1996. I'm just looking through on pro-football-reference, so I could make some mistakes here.

year: winner O-rank/D-rank, loser O-rank/D-rank

1991: Redskins 1/2, Bills 2/18
1992: Cowboys 2/4, Bills 3/14
1993: Cowboys 2/2, Bills 7/5
1994: 49ers 1/6, Chargers 5/9
1995: Cowboys 3/3, Steelers 4/8
1996: Packers 1/1, Patriots 2/12

There's some variation there, obviously, but I'd say overall, this demostrates my point pretty well. Only one team on the entire list was ranked higher in points allowed than in points scored.

Offense wins championships too... just not in this decade.

141
by Fat Tony (not verified) :: Mon, 01/08/2007 - 12:09pm

re: 140 - With the possible exception of the 1994 49ers, it seems all of those champions were strong on both sides of the ball.

Are you more likely to win the SB with a strong defense and a relatively mediocre offense or the converse? Bill's research and conventional wisdom suggest the former. It's hard to see where more detailed analysis of early 90's champs would necessarily contradict that.

What would be the worst offense and worst defense to ever win the Super Bowl?

142
by Pat (not verified) :: Mon, 01/08/2007 - 12:14pm

#140: Uh, you do realize that in that list, every single time the winner was ranked higher in defense than the loser, and several times (Bills, 1991, 1992, Patriots 1996) it was significantly more, whereas for offense, they typically were separated by only a bit.

If you just look at 1996, for instance, clearly, the difference between the 1st ranked offense and the 2nd ranked offense isn't large, but the difference between the 12th ranked defense and the 1st ranked defense is.

To put it another way: the average offensive rank for the SBW in those years was 1.7, and 3.7 for the SBL. The average defensive rank for the SBW was 3, and the defensive rank for the SBL was 11.

That's actually very consistent with Bill's results. It's just going to strengthen his argument. And like I said, it strengthens my point as well - defenses decide championships because in the playoffs, everyone has a half-decent offense.

Treating a 37-17 win as different than a 23-20 win for purposes of predicting *another* game’s outcome is unfounded, until you’ve established the basis for it.

Nonono! I'm not trying to predict another game's outcome (especially not a future game against a different team). I'm trying to predict the same game's outcome. Exact same game. Exact same gameplans. That's the point. And clearly a 37-17 win is less close than a 23-20 game.

doing VOA or any other analysis is “assuming the conclussion�

It is not assuming the conclusion at all. What you'd be doing is finding the teams which have characteristics from the regular season which allow them to put up a high VOA in a playoff game.

Using log5 points scored, you'd be locating team characteristics from the regular season which have historically allowed teams to beat the crap out of teams in the playoffs.

Let me put it this way: suppose you've got a correlation between log5 win percentages in the playoffs and defensive DVOA on first down, and team X has a defensive DVOA on first down of -100%, and that leads to a win percentage in the playoffs which corresponds to an average 14 point margin in favor. And you've got another one involving offensive DVOA, which corresponds to an average 3 point margin in favor.

The assumption you're making here is that in the playoffs, teams that average a 14 point margin in their favor in the playoffs win more in the playoffs than teams that average a 3 point margin in favor in the playoffs.

There is no way anyone can convince me that that's an unreasonable assumption to make. The game doesn't change - if you only average a win by a field goal, the playoffs can end when Tony Romo drops the field goal snap. Matt Cassel could've dropped three and it wouldn't've made a tiny bit of difference.

143
by Pat (not verified) :: Mon, 01/08/2007 - 12:23pm

Nonono! I’m not trying to predict another game’s outcome (especially not a future game against a different team). I’m trying to predict the same game’s outcome.

Poorly stated: I'm not trying to predict anything. I'm trying to replace the win-loss with an indicator which represents the strength of victory. In baseball, this is utterly clear, considering there's a clear separation between offense and defense, for the most part. In football, there's a tiny assumption. But honestly, compared to the other assumptions that are made all the time with sports statistics, it's utterly insignificant.

And it could be checked. But I'd be utterly and completely amazed if it wasn't true. But it would take more statistics than is available, and criticizing an analysis like that for that assumption is really, really nitpicking. You can criticize using won-loss rather than a better metric much easier.

144
by James G (not verified) :: Mon, 01/08/2007 - 12:57pm

139, 140 - I suspect you are right. When I was trying to do my own football analysis, I wrote an article titled "Defense Wins Championships?" (linked through my name) and used the '90s to make my point, just a year before the Ravens clearly won with defense. 1992-1998 saw either the 1st or 2nd best offensive team (according to turnover adjusted yards/drive) win the Super Bowl every year. Defensively? Only Green Bay '96 was ranked 1st (their offense was also ranked 1st). The next best defenses were Denver '97 (5th) and Dallas '92 (5th).

After Baltimore won their Super Bowl, defensive teams started taking charge again.

145
by Bjorn (not verified) :: Mon, 01/08/2007 - 1:15pm

One thing I've been thinking about regarding the FG/XP effectivness of kickers is how to assign blame or credit between the three main people on a field goal attempt (long snapper, holder and kicker). That sometimes either snaps or holds are completly bungled is of course obvious but I have a suspicion that quite a few "normal" misses are due to smaller inperfections of the set up process. Small things at the spot of the kick such as laces in the wrong direction, ball placed ½ an inch wrong, ball spoted late etc probably translate to many feet 30-40 yards downfiel when the ball reaches the goalposts.

146
by chris clark (not verified) :: Mon, 01/08/2007 - 1:32pm

:143 "And it could be checked. But I’d be utterly and completely amazed if it wasn’t true."

So would I, but it is still an assumption. And, yes, it is really nitpicking. However, too many facts are assumed to be "obvious", but when examined turn out to be unsupported.

If FO hadn't challenged some of those truths in football mythology, one would still be arguing that one needs to establish the run to win. Oh, some people still argue that. Well, confront them with the facts.

My point is that Bill's article did that. He took some metric of success in the playoffs and established that some statistics correlated with it. It was important that the metric he chose was not the same as the statistics he was trying to correlate.

Now that that has been done, more advanced analysis is credible. Before that, one could have been building upon the assumption that the earth is flat.

There are still some gaps, like Bill's analysis did not compare playoff VOA's to his metric. However, since the result is not life changing (I don't think my life will be substantially affected by any of the 4 remaining teams winning the SB), I'm willing to gloss over that point somewhat.

Moreover, I don't really doubt that the conclussions one would get if one used VOA as the metric would be valid, at least for the data we have.

I was just trying to point out that for the same reason that VOA is a better stat than the tradition yards gained and allowed statistics, because it better predicts that aspects we really care about, that Bill's analysis was a crucial step to getting the right answers and that you couldn't skip that step. Bill modelled winning the SB and showed that certain stats corresponded to winning the SB in his model.

The thing we get from that is a pointer to which stats are relevant. You even get a lead on how to develop the argument on why the stats are relevant, e.g. that the 97 & 98 Broncos, who were more offensively oriented (and thus appear counter to the conclussions), weren't actually poor defensive teams.

You get all that because there is actually a solid basis for the argument. Otherwise, one is just piling myths on top of myths.

147
by Not saying (not verified) :: Mon, 01/08/2007 - 3:55pm

Re: 142 To put it another way: the average offensive rank for the SBW in those years was 1.7, and 3.7 for the SBL. The average defensive rank for the SBW was 3, and the defensive rank for the SBL was 11.

But wouldn't the super bowl loser have got more than an average number of points just by getting to the super bowl? The example you have of a team with a mediocre defense and good offense getting to the super bowl would seem to go against the theory a bit.

148
by Pat (not verified) :: Mon, 01/08/2007 - 4:11pm

It was important that the metric he chose was not the same as the statistics he was trying to correlate.

That's the part you keep mentioning, and it's not what I'm saying. VOA and DVOA aren't the same thing. DVOA is attempting to distill a metric from games against different opponents. VOA is attempting to distill a metric from a single game.

You might think "big deal, it comes from the same thing" - but that's not important. The two metrics would be completely and totally separate.

And to throw even more wood on my own fire (pillory me! go ahead!) - Bill could've even used DVOA in the playoffs, too. That would've been "which kind of teams are most likely to continue their regular-season performance in the playoffs?" After all, in some sense, we don't want to penalize Indianapolis for constantly running into the eventual Super Bowl winner the previous years.

Correlating DVOA in the regular season to DVOA in the playoffs honestly is fine. The two measures are mostly disjoint, other than a few opponent adjustments, so statistically there's no real problem there (you're not correlating something to itself - there are far more degrees of freedom than their are constraints) - yes, you do lose a bit because "maybe teams weren't playing as hard in the regular season, and playing just to win" - but is that worse than treating Indianapolis's path in the 2004 playoffs as equal to the Vikings' path in 2004?

However, too many facts are assumed to be “obvious�, but when examined turn out to be unsupported.

Yes. But we don't really have the statistics to check this. There isn't enough data to check the winning percentage of teams with a given VOA in playoffs vs in the regular season. Right now it would make more sense to use a reasonable assumption (football games stay roughly the same in the playoffs) to compensate for a known limitation (football games aren't always won by the team which actually played better).

149
by Pat (not verified) :: Mon, 01/08/2007 - 4:13pm

The example you have of a team with a mediocre defense

An 11th ranked defense isn't 'mediocre'. It's borderline top-10.

And we don't know how those teams ranked in the specific breakdowns Bill mentioned above.

150
by doktarr (not verified) :: Mon, 01/08/2007 - 4:38pm

RE: 147,

Exactly. The Pats beat superior defensive teams on the way to REACHING the Super Bowl. So the (relatively) poor defensive clubs beat better defensive clubs, because (surprise, surprise) they had better offenses.

I just looked at every playoff game involving the AFC champion from 1992-1997.

- The team with the superior regular season scoring offense in the game was a collective 18-1.

- The team with the superior regular season scoring defense in the game was a collective 11-8.

I don't see how you could possibly think that supports Bill's point.

In detail:

The 1991 Bills beat the defensively stronger Chiefs (#4) and Broncos (#3) to reach the Superbowl.

The 1992 Bills beat the defensively stronger Oilers (#9), Steelers (#2), and Dolphins (#13, the weakest of the three, yet they made the championship game) to reach the Superbowl.

The 1993 Bills were stronger on both sides of the ball than both of their pre-Superbowl opponents.

The 1994 Chargers provide the only truly contrary data point, as they beat the (defensively inferior, offensively superior) Dolphins. They then beat the defensively superior Steelers (#2).

The 1995 Steelers beat the Bills (worse on both sides of the ball), and then beat the defensively superior Colts (#5).

The 1996 Pats beat the defensively stronger Steelers (Tied #4), and the uniformly inferior Jags, to reach the Super Bowl.

151
by doktarr (not verified) :: Mon, 01/08/2007 - 4:39pm

RE: 147,

Exactly. The Pats beat superior defensive teams on the way to REACHING the Super Bowl. So the (relatively) poor defensive clubs beat better defensive clubs, because (surprise, surprise) they had better offenses.

I just looked at every playoff game involving the AFC champion from 1992-1997.

- The team with the superior regular season scoring offense in the game was a collective 18-1.

- The team with the superior regular season scoring defense in the game was a collective 11-8.

I don't see how you could possibly think that supports Bill's point.

In detail:

The 1991 Bills beat the defensively stronger Chiefs (#4) and Broncos (#3) to reach the Superbowl.

The 1992 Bills beat the defensively stronger Oilers (#9), Steelers (#2), and Dolphins (#13, the weakest of the three, yet they made the championship game) to reach the Superbowl.

The 1993 Bills were stronger on both sides of the ball than both of their pre-Superbowl opponents.

The 1994 Chargers provide the only truly contrary data point, as they beat the (defensively inferior, offensively superior) Dolphins. They then beat the defensively superior Steelers (#2).

The 1995 Steelers beat the Bills (worse on both sides of the ball), and then beat the defensively superior Colts (#5).

The 1996 Pats beat the defensively stronger Steelers (Tied #4), and the uniformly inferior Jags, to reach the Super Bowl.

152
by doktarr (not verified) :: Mon, 01/08/2007 - 4:39pm

RE: 147,

Exactly. The Pats beat superior defensive teams on the way to REACHING the Super Bowl. So the (relatively) poor defensive clubs beat better defensive clubs, because (surprise, surprise) they had better offenses.

I just looked at every playoff game involving the AFC champion from 1992-1997.

- The team with the superior regular season scoring offense in the game was a collective 18-1.

- The team with the superior regular season scoring defense in the game was a collective 11-8.

I don't see how you could possibly think that supports Bill's point.

In detail:

The 1991 Bills beat the defensively stronger Chiefs (#4) and Broncos (#3) to reach the Superbowl.

The 1992 Bills beat the defensively stronger Oilers (#9), Steelers (#2), and Dolphins (#13, the weakest of the three, yet they made the championship game) to reach the Superbowl.

The 1993 Bills were stronger on both sides of the ball than both of their pre-Superbowl opponents.

The 1994 Chargers provide the only truly contrary data point, as they beat the (defensively inferior, offensively superior) Dolphins. They then beat the defensively superior Steelers (#2).

The 1995 Steelers beat the Bills (worse on both sides of the ball), and then beat the defensively superior Colts (#5).

The 1996 Pats beat the defensively stronger Steelers (Tied #4), and the uniformly inferior Jags, to reach the Super Bowl.

153
by Not saying (not verified) :: Mon, 01/08/2007 - 4:42pm

Re: 149 An 11th ranked defense isn’t ‘mediocre’. It’s borderline top-10.

I was thinking of the example of the '96 Pats. Offense 2 by points; defense #14 by points (from here, where'd you get #12?). 14 out of 30 seems mediocre to me.

And we don’t know how those teams ranked in the specific breakdowns Bill mentioned above.

Right, because they're based on DVOA. I was just going off the numbers you gave, which seem to be the best we got for now.

154
by Not saying (not verified) :: Mon, 01/08/2007 - 5:04pm

If you're going by yards the '96 Pats are #20. If you use the stats from James G's site (which seem closer to DVOA, since they include adjustments for turnovers and such based on The Hidden Game although they're drive stats), the Pats are either 15th, 15th, or 11th on D, though they drop down to 9th, 10th, or 5th on O, so maybe their offense wasn't so hot.

155
by chris clark (not verified) :: Mon, 01/08/2007 - 5:35pm

:148 I wrote a longer reply, but trashed it since it wasn't about football.

"Yes. But we don’t really have the statistics to check this."

I think we do have enough data to check some simple conclusions, but only if we define our target metrics to be what we want.

Bill defined PSP to be a measure of playoff success. He was able to see if his measure was correlated with regular season stats and to analyze which ones seemed to influence it.

He could also have done the same thing with playoff VOA. However, one can't argue if one has measured playoff VOA and found the correlations, that those correlations will apply to PSP.

Thus, Bill could have done a good article on "continuing their regular season performance into the playoffs", but it would have been slightly different.

VOA != winning games (to wit the early season Eagles compared to the Colts while they were undefeated), so one needs to be careful what one is correlating against.

156
by Reinhard (not verified) :: Mon, 01/08/2007 - 6:12pm

Not sure if this would make a difference...
a loss is worth -1
a win is worth 1 pt

also, I would be curious to see how those correlations compare to the regular season... I mean, otherwise, there is no way to seperate how strongly these variables compare to winning in general vs winning in the playoffs.

157
by Pat (not verified) :: Mon, 01/08/2007 - 6:16pm

I was thinking of the example of the ‘96 Pats. Offense 2 by points; defense #14 by points (from here, where’d you get #12?). 14 out of 30 seems mediocre to me.

11th is their average rank. Using any one specific team isn't going to work - any year, wacko things can happen. 2001 Patriots, etc.

I don’t see how you could possibly think that supports Bill’s point.

I don't see how you could think that it defeats it. Looking at "who beats who" directly isn't what he was doing. Here's a simple test: what's the average offensive rank for all playoff teams from 1992-1997? What's the offensive rank for the Super Bowl champion? Ditto for defense. (See post #117)

If the difference between the average for all playoff teams and for the Super Bowl champion is smaller for offense than defense, if you repeated Bill's study, you'd very likely get similar results (there's a bit of a technical caveat, but I won't mention it as it's likely unimportant).

You're going to have situations where Team A, with, say, 1/5 offense/defense play Team B with 5/1 offense/defense, and win. Sure. You might even have a bunch of them. But you're going to have more situations with Team A with 1/5 offense/defense beating 2/18 offense/defense than you have 1/5 offense/defense beating 18/2 offense/defense - because the 18/2 team never made it in.

That will give you a correlation. Flat out. It doesn't imply that offense doesn't win you games! Bill didn't do a multivariate regression, I believe. It just implies that the strongest variation which correlates to postseason success is defense - because crappy offense/good defense teams never made it in, and therefore the biggest thing which separates how far teams go in the playoffs is their defense.

VOA != winning games

Yes, but "winning games != deserving to win the game." Which is the entire point. Yes, you'll get situations like Philly/Colts in a game or two in the early part of the year - but who cares? You can't predict Tony Romo dropping the ball on an extra point, or Matt Bryant making a 62-yard field goal. We know you can't predict this stuff. That's just life when you're talking about a game.

There's no reason to artificially limit yourself to wins/losses when we know that the difference between a win and a loss in a close game can be determined by completely random things. Treating a game that's decided by completely non-predictive events as equal to one that was decided over and over by predictive events is just silly.

And besides, if you really don't like VOA (which you keep coming back to), just use points scored and points allowed. A 21-20 game is clearly closer than a 23-8 game, or a 37-16 game. Note that I'm not saying that teams win the Super Bowl by winning blowouts. I'm just saying that a 37-16 win is more repeatable than a 21-20 win. That, we can prove - with preseason, and with regular season. We can't prove it in the postseason, as there aren't rematches. But it's a ridiculously simple assumption to make.

158
by doktarr (not verified) :: Mon, 01/08/2007 - 8:13pm

RE: Pat #157,

You’re going to have situations where Team A, with, say, 1/5 offense/defense play Team B with 5/1 offense/defense, and win. Sure. You might even have a bunch of them. But you’re going to have more situations with Team A with 1/5 offense/defense beating 2/18 offense/defense than you have 1/5 offense/defense beating 18/2 offense/defense

Are you comparing 1/5 beating 2/18 to 1/5 beating 18/2, or 1/5 beating 2/18 to 1/5 beating 5/1? I agree that 18/2 usually isn't in - 2000 and 2002 are exceptions.

But as far as 1/5 beating 2/18 being more common than 1/5 beating 5/1 - do you actually have anything to support that, or are you just making this up? A quick look through the years seems to reveal plenty of more defensively-oriented teams making the playoffs in both decades. It just seems that in the 1990s, the more offensive teams tended to beat them - and in the 2000s, the "pattern" reversed.

As far as this defeating (as you put it) Bill's point: I didn't say it did. I can't and won't draw conclusions based on limited data. But it certainly doesn't SUPPORT what Bill wrote, which is what you argued.

Bill explicitly states the conclusion that "defensive performance is a stronger predictor of playoff success than offensive performance across the board". I continue to think this is just a statistical fluke of the DVOA era, and my back-of-the-envelope analysis of the six preceeding years seems to suggest this as well.

159
by NF (not verified) :: Mon, 01/08/2007 - 8:22pm

What is the correlation between defensive DVOA and offensive DVOA for playoff teams split by points scored? If the two factors are independent it should come out close to zero.

160
by NF (not verified) :: Mon, 01/08/2007 - 8:23pm

I meant playoff points.

161
by Pat (not verified) :: Mon, 01/08/2007 - 8:43pm

Are you comparing 1/5 beating 2/18 to 1/5 beating 18/2, or 1/5 beating 2/18 to 1/5 beating 5/1? I agree that 18/2 usually isn’t in - 2000 and 2002 are exceptions.

No, just comparing 1/5 beating 2/18 to 1/5 beating 18/2. Sorry, I switched from "1/5 vs 5/1" to "1/5 vs 2/18" for no apparent reason.

The fact that 18/2 teams don't get in (but vice-versa do) is important. It means that the average playoff offense is good (better than the average playoff defense is).

But it certainly doesn’t SUPPORT what Bill wrote, which is what you argued.

No no, I'm pretty sure it would. Just looking at the Super Bowl victories - the Super Bowl victories would absolutely support Bill's analysis, and those teams have the largest lever arm on the regression. In those cases, if you just "fuzz" the offensive rankings by, say, +/- 1 ("points scored" doesn't always imply offense, so just fuzz the rankings a bit - that's why that 18-1 record you quoted is likely biased - an "A-" offense and a "A+" defense can have a higher "points scored" than a "A+" offense and a "C-" defense), and likewise for the defensive rankings, you'd see that the best offense doesn't always win, but the best defense always did.

Really, it may seem counterintuitive, because I think you're taking the regression's Bill's quoting to imply "the crappiest offense could win in the playoffs if it's paired with a great defense in these specific areas" and that's not what it's saying at all. The average playoff team already has a great offense.

Bill explicitly states the conclusion that “defensive performance is a stronger predictor of playoff success than offensive performance across the board�.

Part of the problem in what Bill's saying is that you don't really know where, say, the Ravens or the Bears rank offensively. Bill does ranks of all teams this year, but his correlation was all playoff teams, ever. If the Bears, for instance, are the worst playoff offense ever (they're not, but follow me, though last year they might've been) then even if offense is only a weak predictor, it doesn't matter. Even a small effect multiplied by a lot can be significant.

Since the spread on defense is likely much larger than on offense (bad defenses get in with good offenses, not vice versa), the most significant effect is going to be defense - simply because when you look at all the teams in the playoffs, there isn't that much variation in the offenses, and so picking out "which one is the best" is harder, and therefore will be a smaller effect.

162
by Pat (not verified) :: Mon, 01/08/2007 - 8:52pm

#161: Just to point out what I meant regarding "offensive != points scored" - Chicago ranked #3 in scoring offense for the regular season.

Remove non-offensive scores, and they'd rank 11th. And, of course, that doesn't take into account the short offensive scores they also likely had due to their defense.

Scoring offense really folds in defense quite a bit.

163
by NF (not verified) :: Mon, 01/08/2007 - 11:00pm

I don't think 9 Super Bowls champions is a big enough data set to make any reliable conclusions about what helps teams win the Super Bowl. By weighting those teams heavily in an analysis that also intends to find out what helps teams win in the playoffs, a small set at one end of the sample could be confounding the analysis (9 teams with scores ranging from 9 to 14 are the Super Bowl champions, while all other 99 playoff teams have scores ranging from 9 to 0, with at least 36 of those having a score of zero).

If you treat the playoff point total for each team as a non-scale value, with no defined proportions between values, then I don't think the skew is an issue, as long as the playoff points total is an actual ordinal value, with teams having more playoff sucess than another team if they have a higher point total than that team. The 2005 season playoffs in ordinal ranking by the scoring used in the article:

#1: Pittsburg
#2: Carolina
#3: Seattle
#4: Washington
#5: Denver, New England
#7: Chicago, New York, Cincinnati, Indianapolis, Jacksonville, Tampa Bay

One thing I think we can all agree on is that losing the first and only game a team plays is the least desirable playoff outcome regardless of seeding. However, it's debatable whether winning two playoff games on the road and losing in the conference championship is better than winning two at home and losing the Super Bowl.

I think too little is being made of in the article of the fact that the correlation between Total DVOA and the playoff success score is 0.317, higher than any split. I don't know enough statistics to know whether or not an aggregate model of splits can be more accurate than what they are split from if the splits all have a lower correlation than the original variable.

Given that at least a third of all playoff teams fail to win a single game each year, including some teams that have been top teams by DVOA (2005 Colts, 2003 Chiefs, 2000 Bucs), and some teams that have a low DVOA manage to have sucess in the playoffs (1998 Cards, 2001 Patriots, 2003 Panthers, 2004 Rams, 2004 Falcons), why not do an analysis that looks strictly at whether a playoff team won their first game or not.

164
by Pat (not verified) :: Tue, 01/09/2007 - 3:03am

I don’t know enough statistics to know whether or not an aggregate model of splits can be more accurate than what they are split from if the splits all have a lower correlation than the original variable.

Sure it can. Just tells you that some of the splits used correlate independently (and therefore being good in both is better than just one). Some are likely dependent - that is, could be that the entire reason that first down DVOA correlates is because first down passing DVOA correlates, since one is contained in the other. So you can have an aggregate correlate more (which tells you it contains more pertinent information than the subset) or less (which tells you it contains more junk information than the subset).

165
by Not saying (not verified) :: Tue, 01/09/2007 - 1:25pm

11th is their average rank. Using any one specific team isn’t going to work - any year, wacko things can happen. 2001 Patriots, etc.

Fair enough, but it still seems at least a little strange to me that on average 11th ranked teams get to the Super Bowl. 11th out of 30 still isn't that great.

Scoring offense really folds in defense quite a bit.

I think that's where the stats from James G help us out, at least until we get DVOA that far back. There's at least some adjustment made for turnovers, etc.

166
by Pat (not verified) :: Tue, 01/09/2007 - 2:10pm

#165: Yes, but you don't know how many of the 10 teams above them actually made it into the playoffs. Those teams might've had like the 3rd or 4th best defense of all of the teams in the playoffs.

And in addition, since not all teams in the playoffs are guaranteed to have good defenses, you could go through the playoffs never facing anyone worse than you on defense pretty easily only ranked 11th. Philly in 2004, for instance. (2004 is a freaking model year for this argument: a ton of the best defenses - Buffalo, Baltimore, Washington, Miami, Tampa Bay, Jacksonville - never made it in, but the only offenses from 1 to 12 that didn't make it in were Kansas City and Cincinnati).

So, I guess, to put it a different way: want to have the top offense in the playoffs? You better be damn, damn good, every single year. Want to have the best defense in the playoffs? Much less difficult.

167
by Not saying (not verified) :: Tue, 01/09/2007 - 4:17pm

Re: 166

That's true, and definitely goes with the data from James G's article that many of the top defenses don't do well enough in the regular season to make much noise in the playoffs. But that's just the #1s. I don't have time right now to check out all of the numbers.

I'm just saying that this calls for more investigation, not that it's wrong. It looks like a good argument to me. But you can't call up just 2004 after saying that one year can be fluky. Especially not against the argument that the early '90's were different than now.

168
by Pat (not verified) :: Tue, 01/09/2007 - 7:16pm

Oh, I can use other years as examples, too. The only reason I mention 2004 as ideal is because it had a bunch of great offense/bad defense and great defense/bad offense teams, and it's not so obvious without those teams.