by Aaron Schatz

With all four AFC teams currently ahead of all four NFC teams in our ratings, the NFC playoffs are the undercard and the AFC playoffs are the main event. In one corner: the undefeated 16-0 New England Patriots. In the other corner: three very good teams that want to knock them off.

The Jacksonville-New England preview below looks a lot bigger than the San Diego-Indianapolis preview, but the material at the beginning regarding historical teams with large second-half declines applies to both games.

For those who may be visiting this site for the first time to read this preview, we explain our stats at the bottom of the page, or click this link [1]. Each preview also includes a link to the open discussion thread for that game.

Remember that any stats from game charting are incomplete and fairly subjective. Also, the trendlines in the week-to-week charts are somewhat influenced by the wacky "sitting our starters" Week 17 games.

Jacksonville at New England

During the game, please join the discussion in the Jaguars-Patriots Game Discussion Thread [2], for which we absolve ourselves of all responsibility. All vows, obligations, and oaths we have made to keep that discussion thread from drifting into complete insanity are hereby deemed annulled, void, and made of no effect. Read at your own risk.

Based on our weighted DVOA formula which lowers the strength of earlier games to give a more accurate view of how good teams are right now, this game matches up the two best teams in the NFL.

As most fans know, the Patriots haven't dominated over the past few weeks the way they did in September and October, but they still outplayed 15 of their 16 opponents with only one win the system considers "lucky" (against the Ravens). The Patriots offense has been spectacular for the entire season, but the defense has faltered a bit. Through midseason, our DVOA ratings ranked the Patriots fourth in pass defense and 10th in run defense. Since that game, the Patriots rank just 22nd in pass defense and 21st in run defense.

Jacksonville has improved on both sides of the ball since Week 9 -- the week they were blown out by New Orleans with backup Quinn Gray at quarterback. During the first eight games of the year, the Jaguars ranked 10th in pass offense and 14th in run offense. Since Week 10, the Jaguars rank first in pass offense and second in run offense. Yes, that says "first." Contrary to public perception, the Patriots' running game has been more efficient than the Jaguars' running game over the past eight weeks, while the Jaguars have enjoyed the more efficient passing game. The Patriots have the better overall offense because they use the pass much more than the Jaguars do, and teams which pass more generally score more points.

The Jaugars defense has improved as well. Through Week 9, Jacksonville ranked 13th in pass defense and 27 in run defense. Since Week 10, the Jaguars are fourth in pass defense and 14th in run defense.

These trends are so strong that I decided to go back and look at other teams that had a dramatic shift in performance at midseason during the DVOA era (1996-2007). Would this tell us that Jacksonville's second-half surge and New England's (relative) struggles give us a good reason to expect an upset?

I went back and looked at every team with at least 10 wins -- an arbitrary figure, but I wanted to make sure we were only looking at serious Super Bowl contenders. I computed the difference between Weeks 1-9 and Weeks 10-17 on offense and defense. I left out special teams out of pure laziness. (Honesty is the best policy.)

Here are the top 10 biggest declines when we compare Weeks 1-9 to Weeks 10-17.

Notice anything strange about this list? Yes, five of the seven biggest second-half declines by teams that were 10-6 or better took place this year. Was there something in the water? The Patriots didn't even have the largest drop -- the Colts did. Obviously there are reasons for this -- the Colts went through tons of injuries and sat their starters in Week 17 -- but you could point out that teams specifically didn't rest their starters against New England, and bad teams played their hearts out, and besides, this says nothing about whatever happened to Pittsburgh and Dallas.

It may just be a case of regression to the mean, because so many teams started 2007 so strongly -- remember, at one point the Patriots, Colts, Cowboys, and Steelers all ranked among the top 10 teams ever in DVOA through that specific week [3].

Here's the top 10 with the 2007 teams removed, so we can try to learn something here.

The tenth team would actually be the 2003 Dolphins, but I left them out because they didn't make the playoffs.

There are a few teams here that suffered some surprise upsets. The 1996 Broncos lost to the Jaguars. The 2002 Packers lost to the Falcons. The 2005 Bengals don't really count because of the Carson Palmer injury. However, most of these teams just kept going in the playoffs until they lost to a team that was better than them over the entire season anyway, and the Packers won the Super Bowl despite their second half decline.

Here's the opposite list, teams with the biggest second-half improvements.

Again, if the difference between DVOA in Weeks 1-9 and DVOA in Weeks 10-17 is supposed to be an indicator of a possible upset, the numbers are strong for both AFC games, not just one.

At first glance, it looks like we've definitely hit on a list of teams won in the playoffs despite not having the highest DVOA rating for the season: the 1998 Falcons (fifth), the 1997 Packers (fourth), the 2003 Patriots (third). The problem is that those teams all won in years where the top of the ratings were extremely condensed. Atlanta was fifth in a year where the teams ranked between second and fifth were separated by a mere 0.6%. The difference between the 1997 Packers and 1997 49ers was 0.7%. The 2003 Patriots are the only team on this list to win the Super Bowl, but that doesn't really count as a surprise -- the Patriots were only 2.6% behind #1 Kansas City in DVOA, and they had the better won-loss record. After the 2003 Patriots, you have to go down this list by 25 teams or so before you hit the 2001 Patriots, who had the best "second half rise" of any Super Bowl champion. None of the other champions had a "second half rise" of more than 6.5% DVOA.

Even more surprising is the fact that a few teams with huge improvement in the second half of the year were upset by teams that had collapsed during the second half of the year. The best example is 2001. Chicago's DVOA rose by 19.7% between the first and second half of the year. Philadelphia had the largest DVOA drop of any team before 2007. The Eagles went into Chicago and beat the Bears. There are other examples as well. The 2002 49ers (-27.1% drop) beat the 2002 Giants (23.2% rise). The 1998 Broncos (-11.3% drop) beat the 1998 Jets (17.5% rise). And so on.

Numbers are useful because they tell a story, and sometimes the story is that there is no story. There doesn't seem to be any trend where a team that dramatically improved in the second half (such as Jacksonville or San Diego) should be favored to upset a team that was better over the entire season but dropped off in the second half (such as New England or Indianapolis).

And make no mistake -- no matter how well the Jaguars have played recently, New England was still a much better team than Jacksonville over the entire course of the season. Comparing each unit based on rank obscures just how dominant the Patriots' passing game was in 2007. The DVOA difference between the Patriots and the offense ranked second in passing for the year (Indianapolis) was five times larger than the gap between the top two run defenses, seven times larger than the gap between the top two pass defenses, and 15 times larger than the gap between the top two rushing offenses. Of course, the most efficient rushing offense this season also belonged to the New England Patriots.

So with all that in mind, what about the matchups? The Jaguars should run all over the Patriots, right? Aren't they built to win in northern playoff games?

Yes, the Jacksonville running game is good, but it is also inconsistent. The Jaguars were just 18th in Adjusted Line Yards [4] and ranked second in "10+ Yards." If the Patriots want to concentrate on taking away the run, they'll stuff Fred Taylor and Maurice Jones-Drew a lot of the time.

If the Patriots stuff the run on first and second down, they still aren't out of the woods. Jacksonville had the league's best offense in third-and-long situations. However, the Patriots are likely to pressure Garrard, and they will get to him. New England ranked second in Adjusted Sack Rate, while the Jacksonville offensive line was 17th.

Asante Samuel allows just 4.5 yards per pass when listed as the main defender in coverage; the only cornerback who did better (minimum 40 passes) was Roderick Hood of Arizona. Samuel isn't necessarily covering the top receiver for the other team -- in fact, this was the first season since 2003 where the Patriots did not constantly give up huge games to their opponents' number-two receivers. The quality of the Pats' coverage was spread much more evenly between the receiving positions, which is a good thing against a Jacksonville team with no true number-one receiver.

The Pats do need to watch out for situations that leave Tedy Bruschi in pass coverage, where the aging linebacker is a major liability. Our incomplete charting data (through Week 14) has 18 passes listed with Bruschi as the main defender. 15 were complete, and the other three were dropped. Bruschi's Success Rate is 22 percent. (Bruschi has two "official" passes defensed; one was a ball tipped at the line of scrimmage while he was pass-rushing, while the other came against Miami in Week 16.)

Overall, signs point to a Patriots defense that forces a lot of short drives and three-and-outs, but also gives up a couple of huge, embarassing plays when things click for the Jaguars -- a big run or two, a big pass or two. That's a recipe to score points, but it isn't a recipe to hold onto the ball and prevent the Patriots offense from taking the field.

Speaking of which... The Jaguars defense is good, but there's not much reason to believe they can handle the Patriots' attack. Let's start with the secondary. Remember what I said last week about Rashean Mathis: Last year, Mathis had a 57 percent Success Rate and allowed 6.3 yards per pass. In our (incomplete) charting data so far for 2007, Mathis has a 47 percent Success Rate and allows 7.3 yards per pass. If you want standard stats instead, Mathis has dropped from 21 passes defensed and eight interceptions to six passes defensed and one interception. (Yes, Mathis had more interceptions in one playoff game than he did in 16 regular-season games.)

The Jaguars also have trouble with slot receivers [5]. Dallas Clark ate them alive in the two Jaguars-Colts games. Guys like Maurice Stovall, Lance Moore, David Anderson, and Chris "Buster" Davis were racking up first down after first down against the Jaguars with very few incomplete passes. Good luck with Wes Welker.

If the Jaguars come out in a defense designed to slow down the passing game, the Patriots could always run the ball. The Patriots ranked second in Adjusted Line Yards on runs up the middle. The Jaguars defense was 28th. There's no Mike Peterson, no Marcus Stroud, John Henderson is hurt, and Grady Jackson is guaranteed to be winded by the fourth quarter. If the Patriots start by running the ball, and the Jaguars adjust, that opens up the possibility of play-action. The Patriots gained an average of 11.4 yards on play-action passes (or scrambles), the best figure in the league, and the Jaguars give up some big yardage when the offense runs play-action. The Jags gave up 8.2 yards per pass with play-action, higher than the NFL average of 7.4.

A few other notes:

• There is a sense that teams were doing a much better job of pressuring Tom Brady in the last few games of the year, but even if that's true, they still aren't bringing him down very often. The Patriots offense had the same Adjusted Sack Rate before and after their Week 10 bye.
• According to the Football Outsiders Aggressiveness Index, Bill Belichick and Jack Del Rio were two of the league's four most aggressive coaches going for it on fourth down in 2007.
• The Patriots had the league's worst defensive DVOA when the score was within a touchdown in the third quarter ... but the best defensive DVOA when the score was within a touchdown in the fourth.
• The Patriots and Jaguars are the league's top two offenses in terms of time of possession per drive, not counting kneel-down drives. The Patriots held the ball an average of 3:16 per drive, the Jaguars an average of 3:11.
• Here's tomorrow night's forecast [6]: temperatures just above freezing with a wind of four miles per hour. Nobody is going to have a problem throwing the ball.

The Patriots just finished the greatest regular season in the history of professional football. That doesn't guarantee them a title, but it does mean that nobody should expect them to lose until it actually happens. If it does happen, the team to beat them will probably be archrival Indianapolis, not Jacksonville.

San Diego at Indianapolis

During the game, please join the discussion in the Chargers-Colts Game Discussion Thread [7].

San Diego beat Indianapolis 23-21 back in Week 10 thanks to special teams and an injury-decimated Colts offense. The Colts played that game without their starting left tackle and three of their four top receivers. Stuck throwing with Reggie Wayne and a bunch of inexperienced practice-squad types, Peyton Manning had a career-high six interceptions. The Colts' special teams allowed San Diego's Darren Sproles to return both a kickoff and a punt for a touchdown. Despite all this, the Colts nearly pulled out the game with a last-second drive -- until Adam Vinatieri, Mr. Clutch, missed an easy 29-yard field goal.

This time, the injury problems belong to San Diego, not Indianapolis. Left tackle Tony Ugoh, wide receiver Anthony Gonzalez, and tight end Dallas Clark are all healthy for the Colts after missing the first game. The Colts say even future Hall of Famer Marvin Harrison is healthy again after missing 11 games this year.

Clark's return may be the most important. Clark does not actually play tight end most of the time -- he's the Indianapolis slot receiver on virtually all first and second downs. That makes him very important this week, because San Diego's defense ranks seventh against number-one receivers and first against number-two receivers, but 30th against "other receivers." [5] The Chargers gave up big games to guys like Detroit's Mike Furrey, Green Bay's James Jones, and Denver's "Friends of" Glenn Martinez. Nickel corner Drayton Florence is not having a good year, and lost his job to Antonio Cromartie at midseason. Rookie Eric Weddle is a hard hitter, but in general, safety is the Chargers' weakest position.

Meanwhile, the Chargers will probably be without their great tight end, Antonio Gates, due to a toe injury suffered during last week's win over Tennessee. Without Gates, quarterback Philip Rivers loses his security blanket on third down. The Chargers threw to tight ends 38 percent of the time on third down - more than twice the league average of 17 percent.

On first and second down, the Gates injury will affect the Chargers' running game more than their passing game. The Colts were the second-best team in the league at stopping tight ends, thanks in large part to Defensive Player of the Year Bob Sanders. With Gates in the lineup, the Colts would need to use Sanders more in pass coverage. Without Gates, the Colts are free to make Sanders the eighth man in the box on anything that isn't an obvious passing situation. That makes life hard for last year's MVP, running back LaDainian Tomlinson.

(I should note that our injury expert, Will Carroll, believes that the chances of Gates playing are a lot better than the media is reporting [8].)

Bringing Sanders up to the line of scrimmage also helps the Colts with one of their main weaknesses: short-yardage situations. The Colts rank 30th in defensive DVOA on both second-and-short and third-and-short. While the Colts have shown a lot of improvement on defense this year, the front line can still be pushed back when the offense needs just a yard or two. San Diego had one of the NFL's top three offenses on third-and-short.

Despite all the Colts returning from injury, one thing has not changed since the first game: San Diego's dominance on special teams. The Chargers rank fourth in the Football Outsiders special teams ratings [9], above average in every aspect of special teams. Indianapolis ranks last, well below average in everything except punt returns. Adam Vinatieri may be the highest-paid kicker in the league (total contract value) and a possible Hall of Famer, but this year the Colts ranked 29th in net kickoff value and 31st in field-goal kicking.

Other notes:

• According to the Football Outsiders game charting project, San Diego and Indianapolis were the two NFL defenses that blitzed six defenders the least often in 2007. Look at blitzing five, however, and things are very different. San Diego sent exactly five pass rushers more often than any defense in the league, while the Colts still ranked last.
• The Colts had the best defensive DVOA of any team on the road, but they ranked just 19th in defensive DVOA at home. San Diego, on the other hand, ranks first in defensive DVOA at home but just 20th on the road. If you like offense, be happy this game isn't being played at Qualcomm Stadium.
• Marlin Jackson of the Colts ranked fourth among all cornerbacks in run tackles. Kelvin Hayden was tenth. Miami was the only other defense with two cornerbacks in the top ten. On top of that, Bob Sanders was fourth among all safeties in run tackles. So the Indianapolis secondary is certainly ready to take on Mr. Tomlinson.

The Chargers have been hot lately, but remember what I said above in the Patriots-Jaguars preview, and then remember how much of the Colts' second-half decline was tied to all those injuries. Sure, he'll have his usual occasional problems deciphering a 3-4 blitz, but all his weapons to work with, Manning should be able to pick apart that San Diego secondary. If this game is close, the Chargers could definitely win it on a big special teams play. But I think of the four games this weekend, this one is the least likely to be close.

Stats Explained

DVOA (Defense-adjusted Value Over Average) breaks down each play of the season and compares it to the NFL average based on situation and opponent. You'll find it explained further here [10]. Since DVOA measures ability to score, a negative DVOA indicates a better defense and worse offense, and a positive DVOA indicates a better offense and worse defense.

Each team is listed with DVOA for offense and defense, total along with rush and pass, and rank among the 32 teams in parentheses. (If the DVOA values are difficult to understand, it is easy to just look at the ranks.) Red zone DVOA is also listed. These numbers are all regular season only unless noted, with the exception of WEIGHTED DVOA, which is based on a formula which drops the value of games early in the season to get a better idea of how teams are playing now (explained here [11]) and includes the first round of the playoffs.

SPECIAL TEAMS numbers are different; they represent value in points of extra field position gained compared to NFL average. Field goal rating represents points scored compared to average kicker at same distances. All special teams numbers are adjusted by weather and altitude; the total is then translated into DVOA so it can be compared to offense and defense.

Each team also gets a chart showing their performance this year, game-by-game, according to total DVOA. In addition to a line showing each game, another line shows the team's trend for the season, using a third-power polynomial trendline. That's fancy talk for "the curve shifts direction once or twice." The trendline is there to help understand the chart, and shouldn't be seen as a prediction that the team will follow the trendline exactly in the next game.