Writers of Pro Football Prospectus 2008

14 Sep 2012

How Much Time Do You Need for a Late-Game FG Drive?

As is frequently the case with Google, I was in the middle of researching something entirely unrelated, but randomly came across this working paper by a couple of sports management students at the University of San Francisco. They looked at 92 games over the past three NFL seasons wherein a team was either tied or down by one to three points on their final drive, and succeeded at reaching field goal range (i.e., the opponents' 35-yard line). They then built a regression model that predicted how much time (in seconds) it took to get there.

Because of the limitations of the methods they used (which they fully acknowledge in the paper), the results are more explanatory than they are predictive. However, there hasn't been much work done on this kind of question, so what they found is useful as a first step nevertheless. For instance, here are the descriptive stats for the 92 drives:

On average, these teams started the drive at their own 30-yard line with 2:49 left, and down by a score of about 21-19 with two timeouts remaining. Also, teams tended to benefit from the two-minute warning and one other called timeout (offense and defense combined). In terms of player characteristics, successful drives featured a league-average quarterback and one offensive all-pro. Most importantly, it only took these teams 92 teams an average of 80 seconds to reach field goal range. None of this is earth-shattering, but it's good information to know.

The more interesting stuff come from the regression analysis. Results are below:

The analysis says that, on a team's final drive down three or fewer, the amount of time it takes them to reach field goal range is a function of when the drive starts, where the drive starts, how many timeouts the offense has at their disposal, how many timeouts they actually use, and how good their quarterback is. This reeks of "duh" until you look at the regression coefficients, which show some counterintuitive predictions.

I'll start with the least impressive: passer rating. Obviously, we'd love to see them use a better measure of true quarterback skill like DVOA or DYAR. Putting that aside for a moment, though, the regression coefficient is surprisingly positive (i.e., the better your quarterback, the longer it takes to reach field goal range), but essentially meaningless. That's because, according to the model, having a quarterback that's 40 points of passer rating better -- akin to the difference between Tom Brady and Blaine Gabbert last year -- costs a whopping 10 seconds of drive time. Sorry, with 2:49 left, I'll take Brady over Gabbert every day and 100 times on Sunday even if it means my team reaches field goal range with 1:19 left instead of 1:29. Heck, I might even prefer leaving only 1:19 on the clock considering that it means my opponent now has slightly less time than the average it takes to successfully get in position for a field goal of their own (i.e., 80 seconds).

That strategic nuance leads me into the more interesting counterintuitive predictions, which seem to be somewhat conceptually related (although the VIFs say they're not statistically multicollinear). Namely, the earlier a drive starts and the fewer timeouts an offense actually uses, the more quickly they reach field goal range. So, all else equal, a successful field goal drive starting with 2:59 left that uses one timeout reaches field goal range at the 1:06 mark on average, whereas one starting with 2:49 left that uses zero timeouts reaches field goal range at the 1:36 mark (i.e., 30 seconds earlier). What in the name of Norv Turner and Andy Reid is going on here? Why would starting earlier and using more timeouts be associated with longer field goal drives?

I have my suspicions, some of which I've hinted at in the last two paragraphs, but what do you all think? The paper is very readable for an academic write-up, so give it a look and offer your thoughts in the comments.

Posted by: Danny Tuccitto on 14 Sep 2012

12 comments, Last at 17 Sep 2012, 2:09pm by Dan in Philly

Comments

1
by RickD :: Fri, 09/14/2012 - 11:25pm

"Namely, the earlier a drive starts and the fewer timeouts an offense actually uses, the more quickly they reach field goal range"

I think you've got this backwards, at least the second part.

The more quickly a team reaches FG range, the fewer timeouts they'll use, particularly if the drive starts earlier.

3
by Danny Tuccitto :: Fri, 09/14/2012 - 11:37pm

Winner, winner, chicken dinner. Correlation/causation is one of my unmentioned critiques. Wish I had the budget to send you an official FO t-shirt or something.

10
by TimK :: Sat, 09/15/2012 - 6:55pm

Or failing that there is always the XKCD t-shirt that I enjoy wearing to work when the bio-informatics people are about...

http://store.xkcd.com/xkcd/#Correlation

I also wonder if experienced, good, quarterbacks take longer over FG drives because they know how long the final 2 minutes can be and play with an eye on not giving their opponents much time to strike back.

Only looking at successful drives also skews things. Starting further away and with less time will likely more attempts at a big play, so I'd think that would mean the drives will tend to fail (and not be included in the study) of succeed in less time than a more methodical drive with time to work with.

I'd be interested in the proportion of failing drives at different times and distances that run out of time, compared with those that turn the ball over (either takeaways or on downs).

11
by Aaron Brooks Go... :: Sun, 09/16/2012 - 2:24pm

"Only looking at successful drives also skews things."

Potentially drastically, depending on how the pool sizes turn out.

2
by tally :: Fri, 09/14/2012 - 11:32pm

More or less. While these factors do covary with drive time, the drive time is what seems to determine time out usage, for instance. Also, this study only includes those drives that actually succeeded in reaching FG range. While passer rating might vary inversely with drive time, it probably does positively correlate with drive success, which isn't examined here. A better QB will probably shave more time off the clock, as Danny mentions, while here we're only looking at the successful drives of less competent QBs, which might reach FG range while leaving a bit too much time for the opposition.

4
by Dan :: Sat, 09/15/2012 - 3:54am

A better method would be to use whether or not the team reaches FG range as the outcome variable. The main thing to look at is how the probability of reaching FG range varies as the amount of time remaining at the start of the possession decreases. If possessions starting with 3 min left are just as likely to reach FG range as possessions starting with 5 min left, that means that the clock is not a factor with 3 min left - it takes less than 3 min to reach FG range. But at some point, as the amount of time remaining decreases, there is going to be a significant dropoff in probability of reaching FG range, and that tells you how much time it takes to have a late-game FG drive.

You could also see how this varies depending on other factors; timeouts remaining would obviously make a difference (you could see how much time is each timeout equivalent to), and I'd bet that better QBs need less time than worse QBs (in addition to having a higher overall probability of a successful drive).

5
by COINFLIP (not verified) :: Sat, 09/15/2012 - 7:36am

The problem with this study is that it's looking at it backwards. Minimizing the amount of time it takes to get to FG range is not the issue - minimizing the time LEFT after the FG attempt is the critical element.

Which means they should be looking at the failures, as well - games in which too much time was left and the other team was able to score again.

Also, that shades the QB ratings and time-out usage in completely the other direction - effective QBs/coaches aren't necessarily trying to use less time, they are trying to use ALL the time they have efficiently.

So, overall I give the study a C-.

8
by Dean :: Sat, 09/15/2012 - 12:33pm

Even that isn't quite accurate.

Step 1 is getting into field goal rainge in the first place. Only then does minimizing the time left become a priority.

6
by Jimmy :: Sat, 09/15/2012 - 9:12am

Does any of this take into account opposing coaches using timeouts to preserve time on the clock for their offense?

9
by Theo :: Sat, 09/15/2012 - 3:01pm

DEFTOs

7
by james M (not verified) :: Sat, 09/15/2012 - 10:21am

Surely the problem is that they are only looking at successful drives. The fact that drives that start further from field goal range take less time probably means a few big plays got the team the yardage, whereas if you start in good field prosiiton you will probably be more cautious and get there in several low risk plays.

It would be good to see the sucess rate of these FG drives relative to starting field position.

12
by Dan in Philly (not verified) :: Mon, 09/17/2012 - 2:09pm

An idea for a much more interesting study, what are the main positive/negative predictors of late FG drive success? The great thing about something like this is there's little doubt of what is successful and what is failure. So what happens on failed drives that doesn't happen on successful drives?

My guesses of the most significant predictors:
Turnovers (obviously)
Sacks (not only negative yards, but run clock time)
Ability to get out of bounds on almost every play

Unimportant:
Yards per pass (an extra 3 or 4 yards less significant than getting out of bounds)
completion % (lower % might indicate not taking sacks, plus incompletes stop the clock)
yards per rush (again not stopping the clock)

If you looked at a large enough database for these things, I imagine you would find some statistically significant factors, such as taking a sack reduces the odds of a successful drive by 10% or whatever, and this would dictate offensive and defensive strategy (and viewers understanding of such) during games.