Will Adrian Peterson leave Minnesota for a warmer climate in 2015?
29 Jan 2010
by Bill Barnwell
In the NFL, success can be as simple as staying healthy. There have been a million articles written about extra hours of practice and film study yielding surprise playoff appearances, but often those same teams do the same things a year later and lose three or four games more than they did in the previous campaign. Injuries are the NFL's version of Occam's Razor.
While 2009 might have thrown our preseason prediction system for a loop, on the whole, the injury status quo remained the same: The teams that saw a dramatic rise or fall in their health had a commensurate change in their record.
To compile injury data, we use a metric called Adjusted Games Lost (AGL), introduced in Pro Football Prospectus 2008. AGL uses the injury report, the league's various long-term injury lists, and historical rates of participation to measure the level of impact injuries have on a team's starters in a given season. A player listed as Probable, for example, produces a fraction of the AGL that a player listed as Out does, because the historical rate of participation for starters with such injury designations is dramatically different.
The result is a figure representing an estimate of how many "games" each team's starters missed in a given season. AGL is more accurate than simply counting "starter games lost" because, by counting appearances on the injury report, it also accounts for fact that playing hurt means playing at less than full strength. NFL teams recorded an average of 53.9 AGL this season, roughly the equivalent of losing three starters for the entire season in training camp.
These figures begin with the starting lineups as projected at the start of training camps. So a player like Ma'ake Kemoeatu would be included as a starter, even though he never actually started a game this season. We also include a number of "important situational players" for each team, like slot receivers from teams that often go three-wide or situational pass rushers. (Examples include Steve Breaston, Felix Jones, or Bertrand Berry.) Finally, we also adjust the numbers to account for the new starters replacing injured players, factoring in the impact of going from a second-string player to a third-string player. Kickers, punters, and long-snappers are not included.
(For those of you looking for HGL, the metric we introduced in the New York Times this September, you'll have to wait till Football Outsiders Almanac 2010, where we'll be delving even further into our injury research.)
Who was 2009's most injured team, according to AGL?
The Buffalo Bills were the league's most injured team by a wide margin in 2009, beating out the perennially-injured Colts for the top spot. 20 different Buffalo players we considered to be starters, if healthy, missed games during the season. That includes five defensive backs (Donte Whitner, Drayton Florence, Jairus Byrd, Terrence McGee, and Leodis McKelvin) and five offensive linemen (Brad Butler, Demetrius Bell, Eric Wood, Jonathan Scott, and the late-arriving Kendall Simmons).
Speaking of the Colts, it's pretty clear that the Polian Era consistently results in injury rates higher than the league average, likely owing to the team's strategy of fielding an undersized, quicker defense. Fortunately for Indy fans, the Polian Era also has given them a team that drafts better than virtually anyone else in football, so there's not the dropoff that often comes for other teams with injuries. Since 2000, the only time the Colts have had an AGL figure better than league-average is 2005, when they went 14-2 and had the best point differential of the Polian Era.
It's also extremely unusual for the two teams competing in the Super Bowl to rank among the league's least-healthy teams. The Saints aren't perceived as a team that's had to battle through many injuries this year, but they've lost a variety of starters for huge chunks of the season, including fullback Heath Evans (10 games), left tackle Jammal Brown (16), defensive tackles Kendrick Clancy (13 games) and Sedrick Ellis (six), and virtually their entire secondary; Darren Sharper, Jabari Greer, Randall Gay, and Tracy Porter combined to miss 17 starts this season.
On the other side of the coin sit the Denver Broncos, who beat our preseason expectations with some close wins and a remarkable string of health. Broncos starters combined to miss 15 games this season; the two Super Bowl teams each lost more starts than that from just one guy (Jammal Brown, Anthony Gonzalez). Ryan Harris was responsible for eight of those 15 missed starts by himself, thanks to a gruesome-sounding dislocated toe. It's a remarkable total, and it's one not likely to recur, which is why our 2010 projection for Denver is unlikely to be very hopeful.
Among the six healthiest teams were organizations that have made a habit of showing up at the bottom of these lists: Tennessee, Kansas City, and Dallas, whose injury history we detailed in Pro Football Prospectus 2008 and Football Outsiders Almanac 2009. While we've established that injury totals for a team tend to regress to the mean, it's becoming apparent that those organizations might be quantifiably better at keeping their players healthy than the average team. We'll be exploring that issue further in FOA 2010.
The impact of injuries on a team, though, really stands out when we compare the injuries a team had in 2009 to how healthy they were in the previous season. This table does just that, with a positive figure indicating that the team suffered more injuries in 2009 than they did in 2008.
Buffalo was about league-average in 2008, so it's not surprising to see them at the top of this list. While Philadelphia and San Diego were able to improve on their records despite their health issues, Carolina (#2), Miami (#4), Washington (#6), the New York Giants (#7), and Chicago (#9) all fell off and/or didn't meet expectations. In the cases of Carolina and especially Miami, this turnaround was built into their projections. It was also built into our pessimistic projection for the Jets, who managed to overcome an injury to defensive tackle Kris Jenkins and still make it into the playoffs.
The bottom of this list shows the impact staying healthy can have. Denver's second-half woes cost them a playoff spot, but the five next-healthiest teams all made it, including the surprising Bengals. Cincinnati suffered through the most AGL in the history of the metric last year, and while they were still the ninth-most injured team in the league this year, their dramatic improvement drove a significant increase in wins.
Other injury curiosities:
Washington had the most-injured offense in football, with 55.2 AGL on offense alone. They were 22nd on defense. For essentially the second half of the season, they were playing down four offensive starters every week: halfback Clinton Portis (and would-be starter Ladell Betts), tight end Chris Cooley, and offensive linemen Chris Samuels and Randy Thomas.
Jacksonville was the league's healthiest offense. Their only starter to miss time before Week 17 was tackle Maurice Williams, who missed four games. (Tra Thomas, included as a situational player, did miss Week 1.)
Indianapolis topped the defensive injury charts for the second time in three years, with five defensive backs, three linebackers, and both defensive ends missing at least two games.
Denver had the league's healthiest defense. Just behind them was Dallas, whose front seven and starting cornerbacks didn't miss a single start. Safeties Gerald Sensabaugh and Ken Hamlin combined to miss five games.
Please also note that these figures are preliminary, and may differ some from what you see in FOA 2010.
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