2008 AFC Championship Preview

by Aaron Schatz, with injury report by Will Carroll

During the game, please join the discussion in the AFC Championship Game Discussion Thread [1].

For those who may be unfamiliar with the Football Outsiders stats, they are explained at the bottom of the page. Scroll down or click this link [2].

WHEN THE CHARGERS HAVE THE BALL

If the Chargers want to outscore the Patriots, the most important factor is not the game plan or some statistical trend; it is the health of three important offensive players: quarterback Philip Rivers, running back LaDainian Tomlinson, and tight end Antonio Gates. For that, we turn to Will Carroll, who sends in this report:

With Philip Rivers, it is an open question whether he will even take the field. After last week's walk-off performance, Rivers kicked up some rumors that his knee was worse than originally noted, perhaps a torn ACL, but the Chargers quickly dismissed these reports. The evidence isn't on the reports' side either; Rivers has been wearing a type of brace that limits lateral instability. It would do almost nothing for an ACL. No, Rivers is just dealing with a loose knee, one that's just unstable enough that he can feel it when he plants -- and on those occasions when it opens up, it's uncomfortable enough that he can feel the pain in his future.

There's no change in the status of Antonio Gates. Just like last week, he's expected to play by the grace of Xylocaine [3]. Once again, he's more decoy than weapon, but it's a powerful decoy. He should be a bit more effective at the start of the game (and perhaps second half) than the end, but he will occupy a safety when he's in.

LaDainian Tomlinson got a bit lucky. A mild hyperextension and some bruising on the internal aspect of his knee is all he came away with. Slow motion replays show just how close it was to something worse, as his cleats weren't quite down and didn't quite catch a seam. If he's affected at all -- and there's some debate on how completely he could heal in a week -- it will be on stops more than any other part of his game. The Chargers are expected to sub in for Tomlinson more than normal due to weather and offensive packages, so the injury's impact will be dulled.

Will has a good point here -- as talented as Tomlinson is, his injury actually affects the Chargers the least for two reasons. First, it is the least painful of the three injuries. Second, Tomlinson's backups are much better than Billy Volek or whatever third tight end would come into two-tight end packages alongside Brandon Manumaleuma.

It doesn't seem that way if you look only at the 2007 numbers, but it is safe to say that Michael Turner's poor 2007 stats suffer from small sample size. He's neither the best running back in the league, as his 2006 stats showed, or the worst, which is what his 2007 stats show [4].

We like to think of San Diego has an up-the-gut running team, but the Adjusted Line Yards numbers [5] show they were much better this year when running around the ends. They ranked 12th and 11th running around the sides, but 22nd or lower running left tackle, middle, or right tackle.

Normally, a team known for its running backs would build its offense around consistent first-down gains, but that's not the case in San Diego. The Chargers gained an average of just 4.7 yards on first down -- only Chicago, Kansas City, and San Francisco were worse. (The Patriots allowed a league-average 5.4 yards per first down.)

Of course, if there aren't a lot of yards on first down, you end up with second-and-long. And in that situation, the Chargers offense was very good (ninth in DVOA) and the Patriots defense had problems (20th in DVOA). The Chargers gained an average of 8.7 yards when throwing the ball on second-and-10-or-more, more than any other offense.

Another surprising stat about San Diego: Although opposing defenses fear the run, the Chargers were surprisingly mediocre when they used play-action fakes. They averaged just 6.3 yards per play with play-action, 23rd in the league. The Patriots defense was good at sniffing out fakes, allowing just 6.2 yards on plays with play-action fakes, eighth in the league. (Note: I don't have DVOA on the charting spreadsheet yet, which is why I'm giving yardage and not DVOA here.)

The Chargers won their last two games with a lot of deep passes, particularly deep outs and other routes along the sidelines. The Patriots were a fairly average defense against deep passes this year. When it came to short passes, the Patriots were worse than average against passes up the middle, but better than average against passes marked "short left," or "short right." Taking advantage of this would mean a change in San Diego's general offensive game plan. During the regular season, the Chargers threw only 21 percent of passes to the middle of the field, one of the lowest percentages in the league.

Don't be surprised if the Chargers have trouble getting long drives going, because their offense was much better in 2007 when it started with a short field. When they were in their own territory, the Chargers ranked 23rd in offensive DVOA. From the 50-yard line onwards, they ranked fifth. The Patriots defense was the exact opposite: it ranked second in defensive DVOA when the opponent was on its own side of the field, but 25th in defensive DVOA in Patriots territory.

It's pointless to go into a long, drawn-out discussion of Billy Volek vs. Philip Rivers, because we just haven't seen much of Volek over the last couple years. If Volek starts and the announcers talk about all the yardage he put up back in 2004, click on our 2004 quarterback stats [6] and notice the COLOSSAL difference between Volek's numbers with and without the opponent adjustments.

A couple other notes from last week's previews, which might come into play here:

• 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. Ellis Hobbs' numbers are close to league average for cornerbacks.

• The Pats 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.)

• 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.
• If Gates is still hobbled, or can't play, 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.

WHEN THE PATRIOTS HAVE THE BALL

What is left to say about the Patriots' offense? They do everything well, and whatever the defense stops, they'll do something else. They can beat you deep, they can pick at you with short passes, they can run at you. The question becomes: Where are San Diego's defensive strengths and weaknesses, and how will they use those to counter the Patriots' offense and keep them from scoring another 38 points?

The first thing we're going to hear about is the Chargers' ability to pressure Tom Brady. I'm not so sure about that. 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 weren't bringing him down very often. The Patriots offense had the same Adjusted Sack Rate before and after their Week 10 bye. In addition, although we think of San Diego as having a strong pass rush, it was only slightly-above average in 2007, 12th in Adjusted Sack Rate [7]. 

The Chargers' blitz is also remarkably predictable. Usually, one of the strengths of the 3-4 defense is the ability to hide your pass rushers -- you never know which one or two linebackers are coming, and that's before we include the possibility of zone blitzes. But the Chargers don't use their 3-4 this way. In general, we know who is coming: outside linebackers Shawne Merriman and Shaun Phillips. The Chargers rush five more often than any other defense, but rush six or more less often than any team except Indianapolis. Through Week 15, our charters had marked only seven plays where either Merriman or Phillips was the defender in coverage, compared to 45 plays with either Matt Wilhelm or Stephen Cooper in coverage. Coverage responsibilities for 3-4 defenses like Pittsburgh or New England were much more evenly distributed among both inside and outside linebackers.

(I should note that the first San Diego-New England game was one of the few games where the Chargers clearly did bring pressure with the inside linebackers; there were a few plays where Merriman and Cooper rushed Tom Brady while Phillips dropped into coverage.)

One of the big questions will be how often the Patriots make sure to leave a running back or tight end in to account for those five pass rushers, and how often they send five receivers into patterns and trust the offensive line to take on the defenders one-on-one. Our charting data says that when the defense sent five, offenses only left five back to block 22 percent of the time. When the defense sent five against New England, the Patriots left just five back to block 38 percent of the time, almost twice the league average.

Ron Jaworski has talked a lot this year about Tom Brady being blitzed more often than any other quarterback in football. Our charting numbers disagree. This could have something to do with the difference between our definition of a blitz and the definition used by STATS Inc. (where Jaws gets his numbers). Since we ask charters to mark strictly the number of pass rushers, a lot of zone blitzes don't count as blitzes. (I plan to add a "zone blitz" check-off category in 2008.) Anyway, by our numbers, New England faced five or more pass rushers 36 percent of the time, which ranked eighth among offenses. Here's how Brady did against the blitz compared to a normal pass rush. I don't have DVOA here, but I do have offensive "success rate," based on the usual FO benchmarks. This includes sacks and scrambles:

In case you needed evidence that Tom Brady knows how to check down and keep the chains moving when the defense blitzes, well, there you go. The more pass rushers you send, the fewer average yards the Patriots gain on the play. But when you send a big blitz, Brady will throw shorter passes and gain more first downs.

The Chargers ranked seventh in DVOA against number-one receivers, first against number twos, but 30th against "other receivers." [8] The San Diego pass defense dramatically improved at midseason against the starting receivers, but only slightly against "other receivers." None of San Diego's many interceptions came on passes to "other receivers." These "defense vs. receiver types" stats are often the result of scheme, but here it seems very clearly to be an issue of personnel. When Shawne Merriman does need to drop into coverage, he generally looks lost. Safety is clearly the biggest weakness on the team -- Marlon McCree, Clinton Hart, and Eric Weddle are hitters, not cover guys. And while starting cornerbacks Antonio Cromartie and Quentin Jammer had reasonable years, Drayton Florence, did not...

(To answer your question: Yes, I am also surprised that Cromartie's charting metrics are not better.)

New England's advantage over the San Diego defense may be bigger on the ground than it is through the air. The Patriots led the league in offensive Adjusted Line Yards [5], while the Chargers were 29th on defense [7]. However, San Diego's run defense improved significantly over the second half of the season. Through Week 9, the week the Chargers gave up the NFL single-game rushing record to Adrian Peterson, their defense ranked 30th in ALY. Since Week 10, they rank 20th. Also note that it is easier to run to the left against the Chargers than it is to run to the right.

All that running leads to play-action, but this is where San Diego really shines. The Patriots offense averaged 11.1 yards using play action, best in the league. However, the Chargers defense allowed only 4.1 yards on average, also the best in the league. Teams only used play-action on 15 percent of pass plays against San Diego; the only defenses to see it less often were Baltimore and Arizona.

Additional notes:

• The Patriots and Chargers were the league's top two offenses in the red zone, according to DVOA. The Chargers also had the league's top defense in the red zone, which is astounding considering they had the league's worst red zone defense in 2006. The Chargers also had the league's best defense in the next 20-yard area, when the opponent was between 21 and 40 yards from the goal line. New England's offense ranked fourth between the opponents' 21- and 40-yard lines. The Colts, who the Chargers beat last week, ranked first in that area.
• The Chargers were average in penalties on both sides of the ball, while the Patriots were one of the league's least-penalized teams (28th). The only specific thing to look for is that Randy Moss, as most people might guess, led the league in offensive pass interference. Moss was flagged five times, as was Kellen Winslow of Cleveland. No other player was flagged for OPI more than twice, so perhaps the league needs to figure out if it was holding Moss and Winslow to a different standard than everyone else.
• If the game is close at halftime, that doesn't mean it will be close at the end. San Diego's defense ranked second in the first half of games, but 16th in the second half of games.

SPECIAL TEAMS

Both special teams are strong, although the Chargers are superior both on punts (with Mike Scifres) and punt returns (with Darren Sproles). Of course, the Patriots don't plan on actually using their punter very much. It's also worth noting that while these teams ranked second and third in net kickoff value, they did it in different ways. The Patriots have Stephen Gostkowski, one of the top two or thee kickoff men in the league, and good coverage. Nate Kaeding (and Dave Rayner) were average on kickoffs this year, but the Chargers had exceptional kickoff coverage.

WEATHER

Forget any talk about the weather being a positive for the Chargers and a negative for the Patriots. First of all, the Chargers are still the warm weather team that isn't used to playing in cold temperatures; offensive style isn't going to change that. Second, the Chargers' passing game has been heavily dependent on the deep pass in recent weeks, and any wind strong enough to hamper the Patriots' deep passing game is strong enough to hamper the Chargers' deep passing game as well.

OUTLOOK

Like I said on the Bill Simmons podcast [9]: I'm trying to not wear my Patriots-colored glasses here, but this game looks like the most likely blowout on the Patriots' way to 19-0 -- particularly if Billy Volek or a hobbled Philip Rivers throw a couple of early picks. The Chargers' pass rush will get to Brady a couple of times, but most of the time he's going to have time to throw and some big holes in the secondary to throw at. The biggest reason to believe it won't be a blowout is the Chargers' red zone defense, which could force Stephen Gostkowski onto the field numerous times.

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. WEI DVOA is 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]). All numbers are regular season only except for WEIGHTED DVOA, unless noted.

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." Note that even though the chart appears in the section for when each team has the ball, it represents total performance, not just offense.