by Aaron Schatz

New England is back on top this week, as the 49ers drop into third place after losing to St. Louis. Denver is number two, and these three teams have been ranked one, two, and three in some order every week since Week 8 except for after Week 10, when San Francisco briefly dropped to six after the first St. Louis game. The team that broke into the top three that week was Seattle, which now ranks fourth. These four teams are all above 30% and there is a reasonably sized gap between them and the rest of the league. Of course, the fact that San Francisco and Seattle have to compete for the same division title means that neither team is near the top of our Super Bowl odds. The AFC big three of New England, Denver, and Houston rank one to three... followed by six different NFC teams.

One of those six NFC teams is Chicago, but the Bears' calling card, their historically great defense, has declined over the last three weeks. It's still historically great, but not to quite the same extent. Three weeks ago, the Bears' defense was at -39.9%, the second-best ever through 10 weeks. Now the Bears defense is at -29.2%, the sixth-best ever through 13 weeks. Perhaps you noticed in Quick Reads that Russell Wilson had the highest DYAR of any rookie quarterback in DVOA history this week. The adjustments for playing the Bears defense are high, but they're not as high as they would have been three weeks ago, in part because of Wilson's success this week. The Bears played seven games between Week 3 and Week 10. In each of those games, the Bears had defensive DVOA better than -25%. In their last three games, the Bears have defensive DVOA of 1% (SF), -22% (MIN), and 8% (SEA). That's not particularly bad, but it isn't as good as the Bears were playing before, and with their offense, average or even slightly above-average defense just isn't gonna cut it.

A couple of hours ago I posed the question to readers on Twitter: Can anyone think of specific personnel reasons why the Bears defense has been much worse since Week 11? Obviously, there are plenty of non-personnel reasons, starting with simple regression towards the mean. This could all just be the usual random variation, and they just happened to have three weaker games in a row instead of spreading them out. Their strong defensive rating was also built on a lot of turnovers, and we know that a big turnover margin is unsustainable for a long time, but it isn't like the Bears have been giving up tons of yards and living off only turnovers. The Bears were allowing 4.9 yards per play through Week 10, and that has gone up to 5.7 yards per play since, so the issue is not just one of turnovers.

A number of readers brought up that they aren't bringing the same kind of pass pressure recently. There does seem to be some indication of this. I don't have updated pass pressure numbers yet, but Chicago's Adjusted Sack Rate has dropped from 7.3% in Weeks 1-10 to 4.4% in Weeks 11-13,. They've gone from 2.9 sacks per game to 2.0 sacks per game, and the drop in ASR is even larger because of the opponent adjustments (San Francisco has the worst offensive ASR in the league this season). A number of people who responded to me on Twitter specifically picked out Julius Peppers as a player who doesn't seem to be having the same kind of success in recent weeks.

Some people suggested that the Bears' Cover-2 is simply built to stop passing games, not running games, and they've dealt the last three games with three strong running teams. The problem with this is a) the Bears don't actually play Cover-2 as their primary coverage scheme anymore, and b) Houston is a great running team, and the Bears had a great defensive game against them even though the team lost 13-7.

Lots of people brought up age, and the idea that an older defense will decline later in the season as players get tired and start to deal with nagging injuries. This is definitely an idea worth testing, but unfortunately I don't have time to do it this afternoon. However, there is a defense older that Chicago's -- Pittsburgh, where the Steelers' defense has improved dramatically over the last few weeks instead of getting worse due to age. I checked just a couple of other old defenses, and didn't find a trend of late-season decline. The Steelers' defense also got better in the second half of last year. In 2010, both Pittsburgh and Denver had defensive starting lineups that averaged over 30 years old, older than this year's Bears, and both defenses improved slightly in the second half of the season. (Yes, Pittsburgh's defense has been pretty old for a while, although they bring in a new starter or two every year.) The 2000 Panthers and 2006 Dolphins are two other defenses that averaged over 30, and they were basically the same in the first and second half of those seasons.

However, even if it isn't as simple as age = injuries = decline, it is true that the Bears are dealing with some defensive injuries. Readers specifically picked out issues with Charles Tillman, Brian Urlacher, Lance Briggs, and Chris Conte. Conte got hurt early in this week's game, and replacement Craig Steltz had problems, although that doesn't explain the other two games. Tillman was listed as probable with a shoulder injury last week, and of course, he's not getting his usual sleep. (I know people laugh when you point out that a player's performance dips right after he brings home a newborn baby, but we are talking about something that significantly affects your health and sleep schedule.) But if Tillman had an injury before that, it wasn't important enough to put on the injury report. Briggs has been probable for two weeks, but he has also played. Urlacher's injury is going to be a bigger problem going forward -- he was listed as probable with a hamstring injury last week, but then he heard it "pop" late in the Seattle game and apparently he's going to be out the next three or four games. Tim Jennings also hurt his shoulder during the game and will miss the next couple of games. These are actually the first major injuries for the Chicago defense; over the last three weeks, any defensive players on the injury report (Tillman, Briggs, Stephen Paea, Shea McClellin, etc.) were listed as probable.

It could be that the offense is hurting the defense. It's conventional wisdom that when the offense doesn't get a lot of time of possession, the defense suffers because it gets tired. That's another one of those issues that I've always meant to study, although you would need to control to make sure that you were controlling for the quality of the defense overall. Between that and the old defense issue, we may have a nice framework here for the Chicago chapter in next year's book. You're welcome, Rivers.

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The Chicago pass defense and run defense have declined about the same amount. We don't have defensive coverage numbers yet (again, we're stuck because of our lack of financial resources and dependence on volunteers for game charting) but the "defense vs. receivers" numbers do show some indication of the issues. Chicago's coverage on "other receivers" and running backs in the passing game has stayed the same, but their DVOA against tight ends has gotten worse, and their DVOA against No. 1 and No. 2 receivers has gotten much worse. Looking at sides, the DVOA on passes to the left side has declined a lot more than DVOA on passes to the right side. That would seem to suggest that Tillman has struggled more than Jennings in recent weeks. Here are the numbers, which all include Defensive Pass Interference as part of yardage totals and DVOA:

Chicago Bears Pass Defense, Weeks 1-10 vs. Weeks 11-13 Weeks 1-10 Weeks 11-13 Receiver DVOA C% Yd/Pass Receiver DVOA C% Yd/Pass WR1 -45.4% 50% 6.7 WR1 16.9% 64% 9.3 WR2 -31.2% 47% 7.1 WR2 31.5% 62% 10.9 Other WR -51.2% 58% 6.5 Other WR -22.3% 53% 6.1 TE -44.5% 68% 5.9 TE -4.2% 53% 5.7 RB -27.0% 80% 5.0 RB -19.2% 80% 4.7 Direction DVOA C% Yd/Pass Direction DVOA C% Yd/Pass Left -34.9% 61% 6.4 Left 31.0% 69% 9.3 Middle -32.0% 62% 7.5 Middle -50.6% 47% 4.9 Right -53.2% 57% 5.2 Right -20.8% 56% 5.3

Obviously, we can't say what will happen with the Bears defense over the next few weeks. My guess is that Tillman and Peppers will play better but the team won't return to their previous level because a) it was ridiculously good and b) Urlacher and Jennings are hurt. Of course, I'm talking here about FO adjusted numbers -- if you don't adjust for opponent, I'm sure the Bears defense will look awesome just by virtue of getting to play Arizona once.

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BEST DVOA EVER (OR AT LEAST SINCE 1991) WATCH

BEST TOTAL DVOA

THROUGH WEEK 13 x BEST OFFENSIVE DVOA

THROUGH WEEK 13 x BEST DEFENSIVE DVOA

THROUGH WEEK 13 x BEST ST DVOA

THROUGH WEEK 13 Year Team DVOA x Year Team DVOA x Year Team DVOA x Year Team DVOA 2007 NE 62.5% x 2007 NE 47.3% x 2002 TB -39.5% x 2012 BAL 11.5% 1991 WAS 56.6% x 2010 NE 43.2% x 1991 PHI -36.5% x 2007 CHI 11.3% 1998 DEN 47.1% x 1993 SF 40.7% x 1991 NO -31.6% x 2011 CHI 11.0% 2004 PIT 44.1% x 2004 IND 39.5% x 2008 BAL -30.8% x 1994 CLE1 10.9% 2004 PHI 42.9% x 1998 DEN 39.4% x 1997 SF -30.3% x 2004 BUF 10.8% 1999 STL 41.6% x 2002 KC 38.1% x 2012 CHI -29.2% x 1996 CAR 10.5% 1995 SF 41.2% x 1995 DAL 35.8% x 2006 CHI -28.7% x 1998 DAL 10.3% 2004 NE 41.2% x 1992 SF 35.5% x 1995 SF -27.9% x 2001 PHI 10.1% 1994 DAL 40.8% x 2012 NE 34.0% x 2005 CHI -27.4% x 1997 DAL 9.8% 1997 SF 40.4% x 2011 GB 32.5% x 2007 PIT -25.5% x 1993 GB 9.5% 2007 DAL 39.0% x 2005 SD 32.2% x 2004 PIT -25.2% x 2002 NO 9.5% 2012 NE 38.9% x 2005 CIN 31.3% x 2008 PIT -24.8% x 2000 MIA 9.0%

As noted above, the Bears are dropping down this table a bit, but Baltimore's special teams are back on top.

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These are the Football Outsiders team efficiency ratings through 13 weeks of 2012, measured by our proprietary Defense-adjusted Value Over Average (DVOA) system that breaks down every single play and compares a team's performance to the league average based on situation in order to determine value over average. (Explained further here.)

OFFENSE and DEFENSE DVOA are adjusted to consider all fumbles, kept or lost, as equal value. SPECIAL TEAMS DVOA is adjusted for type of stadium (warm, cold, dome, Denver) and week of season. WEIGHTED DVOA represents an attempt to figure out how a team is playing right now, as opposed to over the season as a whole, by making recent games more important than earlier games. As always, positive numbers represent more points so DEFENSE is better when it is NEGATIVE.

To save people some time, please use the following format for all complaints:

<team> is clearly ranked <too high/too low> because <reason unrelated to DVOA>. <subjective ranking system> is way better than this. <unrelated team-supporting or -denigrating comment, preferably with poor spelling and/or chat-acceptable spelling>

All stats pages should now be updated, including snap counts. FO Premium will be updated later tonight.

TEAM TOTAL

DVOA LAST

WEEK WEIGHTED

DVOA RANK W-L OFFENSE

DVOA OFF.

RANK DEFENSE

DVOA DEF.

RANK S.T.

DVOA S.T.

RANK 1 NE 38.9% 2 39.7% 1 9-3 34.0% 1 1.7% 18 6.6% 2 2 DEN 37.0% 3 38.1% 2 9-3 19.2% 2 -15.4% 5 2.4% 10 3 SF 35.1% 1 32.2% 4 8-3-1 18.8% 3 -17.3% 3 -1.0% 23 4 SEA 31.9% 4 35.6% 3 7-5 12.9% 5 -12.8% 6 6.1% 3 5 GB 23.7% 6 22.3% 5 8-4 16.2% 4 -6.5% 7 1.0% 12 6 CHI 22.2% 5 20.2% 6 8-4 -13.1% 26 -29.2% 1 6.1% 4 7 HOU 18.6% 8 16.4% 8 11-1 6.8% 11 -18.0% 2 -6.1% 31 8 NYG 16.5% 7 18.4% 7 7-5 12.2% 6 -3.8% 12 0.5% 15 9 BAL 12.6% 9 9.6% 10 9-3 2.7% 14 1.6% 17 11.5% 1 10 ATL 6.3% 12 2.1% 14 11-1 1.9% 16 -3.7% 13 0.8% 13 11 WAS 4.3% 14 7.1% 11 6-6 11.8% 7 3.1% 20 -4.3% 28 12 CIN 3.0% 10 11.0% 9 7-5 4.3% 12 4.6% 22 3.3% 9 13 TB 2.7% 13 2.9% 12 6-6 7.9% 10 0.5% 16 -4.7% 29 14 DET 0.9% 11 0.8% 15 4-8 11.4% 8 6.3% 24 -4.1% 27 15 PIT -0.4% 18 2.7% 13 7-5 -4.5% 20 -4.0% 11 0.2% 16 16 DAL -2.0% 15 -3.9% 19 6-6 3.9% 13 4.6% 23 -1.2% 24 TEAM TOTAL

DVOA LAST

WEEK WEIGHTED

DVOA RANK W-L OFFENSE

DVOA OFF.

RANK DEFENSE

DVOA DEF.

RANK S.T.

DVOA S.T.

RANK 17 NO -3.1% 16 -1.1% 16 5-7 8.6% 9 15.5% 30 3.8% 8 18 CAR -3.5% 19 -2.0% 18 3-9 2.2% 15 -1.3% 14 -7.0% 32 19 MIN -4.0% 17 -7.6% 23 6-6 -3.9% 19 4.5% 21 4.5% 5 20 STL -4.3% 21 -4.5% 20 5-6-1 -6.4% 21 -4.7% 9 -2.6% 26 21 MIA -5.3% 20 -6.6% 21 5-7 -10.8% 24 -4.3% 10 1.3% 11 22 BUF -7.1% 23 -1.3% 17 5-7 -1.8% 18 9.8% 26 4.4% 6 23 SD -8.3% 24 -6.8% 22 4-8 -9.0% 22 -1.0% 15 -0.3% 20 24 ARI -9.4% 22 -10.8% 25 4-8 -26.7% 32 -17.2% 4 0.1% 17 25 NYJ -10.6% 26 -11.3% 26 5-7 -15.9% 29 -5.6% 8 -0.3% 19 26 CLE -13.6% 25 -10.0% 24 4-8 -15.7% 28 2.1% 19 4.1% 7 27 PHI -18.9% 27 -21.4% 28 3-9 -11.4% 25 7.5% 25 -0.1% 18 28 IND -19.6% 28 -19.2% 27 8-4 -0.2% 17 17.9% 31 -1.6% 25 29 TEN -28.9% 29 -26.6% 29 4-8 -14.8% 27 13.0% 27 -1.0% 22 30 JAC -34.4% 30 -33.2% 30 2-10 -20.6% 30 13.2% 28 -0.6% 21 31 OAK -34.6% 31 -34.9% 32 3-9 -9.1% 23 19.5% 32 -6.0% 30 32 KC -35.8% 32 -33.8% 31 2-10 -22.1% 31 14.3% 29 0.6% 14

NON-ADJUSTED TOTAL DVOA does not include the adjustments for opponent strength or the adjustments for weather and altitude in special teams, and only penalizes offenses for lost fumbles rather than all fumbles.

does not include the adjustments for opponent strength or the adjustments for weather and altitude in special teams, and only penalizes offenses for lost fumbles rather than all fumbles. ESTIMATED WINS uses a statistic known as "Forest Index" that emphasizes consistency as well as DVOA in the most important specific situations: red zone defense, first quarter offense, and performance in the second half when the score is close. It then projects a number of wins adjusted to a league-average schedule and a league-average rate of recovering fumbles. Teams that have had their bye week are projected as if they had played one game per week.

uses a statistic known as "Forest Index" that emphasizes consistency as well as DVOA in the most important specific situations: red zone defense, first quarter offense, and performance in the second half when the score is close. It then projects a number of wins adjusted to a league-average schedule and a league-average rate of recovering fumbles. Teams that have had their bye week are projected as if they had played one game per week. PAST SCHEDULE lists average DVOA of opponents played this season, ranked from hardest schedule (#1, most positive) to easiest schedule (#32, most negative). It is not adjusted for which games are home or road.

lists average DVOA of opponents played this season, ranked from hardest schedule (#1, most positive) to easiest schedule (#32, most negative). It is not adjusted for which games are home or road. FUTURE SCHEDULE lists average DVOA of opponents still left to play this season, ranked from hardest schedule (#1, most positive) to easiest schedule (#32, most negative). It is not adjusted for which games are home or road.

lists average DVOA of opponents still left to play this season, ranked from hardest schedule (#1, most positive) to easiest schedule (#32, most negative). It is not adjusted for which games are home or road. VARIANCE measures the statistical variance of the team's weekly DVOA performance. Teams are ranked from most consistent (#1, lowest variance) to least consistent (#32, highest variance).