by Danny Tuccitto

Peyton Manning's degenerating cervical disc and subsequent surgery dominated headlines and had far-reaching implications during the 2011 season -- and subsequent offseason -- like no other injury situation in recent NFL history. We've all had the details drilled into our heads over the past year, so I won't recap them here, but suffice it to say that enough dominos fell to have a decent-sized double-sixes tournament. Looking back, not even Tom Brady's knee injury in 2008 ended up meaning so much to so many cities.

Seemingly lost in all the hoopla surrounding Manning, though, was that plenty of other teams saw their fates determined in part by player health (or lack thereof). For instance, just ask Texans fans what they think might have been if Matt Schaub's foot injury -- and let's not forget Matt Leinart's noncompliant collarbone -- didn't force fifth-round rookie T.J. Yates into the starting lineup during their playoff run. In contrast, the 49ers' unexpected ascension into the NFL elite probably would not have happened if their "shallow chart" on defense didn't benefit from an almost pristine injury record.

Of course, every fan base plays the what-if game after their team's season is over, and injuries usually play a central role in the game. Sometimes blaming injuries is justified, and other times it isn't, so let's put some hard data to use here. Using Football Outsiders' adjusted games lost (AGL) metric, let's find out which teams were most (and least) infected with the injury bug during the 2011 regular season.

To refresh memories, the key ideas underlying AGL are that all players don't affect winning and losing equally, and missing a game isn't the only way a player injury affects winning and losing. Injuries to starters, important situational reserves (e.g., nickel cornerbacks), and injury replacements (i.e., new permanent starters) count towards AGL, whereas injuries to benchwarmers don't. Similarly, injuries that land a player on injured reserve affect AGL more than injuries that force a player to be listed as "questionable," which in turn affect AGL more than injuries that lead to a "probable" game status.

Before we get into last season's AGL totals for specific teams, let's first look at a few leaguewide trends that have emerged over the past few years, the most glaring of which has to do with the sheer amount of AGL that teams have been experiencing over the course of the past decade. Below is a graph showing the trajectory of aggregated AGL over time across the entire NFL.

Essentially, injuries cost players nearly double the number of AGL in 2011 as they did in 2002. Converting the numbers in the graph to team averages, we're talking about the average team losing 60.5 adjusted games due to injury last season, as opposed to 33.6 a decade ago. That's the equivalent of having an additional two important players miss an entire season.

The obvious question here is, "Why?" Certainly, if we focus only on the one-year increase from 2010 to 2011, there's a pretty obvious culprit: the lockout. Of course, it stands to reason that the league's increased emphasis on player safety should have at least resulted in less steep of an increase. There's also the possibility -- close to a statistician's heart -- that 2011 was just a random fluctuation.

Whatever the reason for last season's uptick, the increasing trend over a 10-year period -- or even a seven-year period if you want to look at it that way -- is unmistakable. For the long-term trend, we have several hypotheses that we're in the process of fleshing out, which you'll likely see addressed in Football Outsiders Almanac 2012 (available in July). They include, but of course are not limited to, the following: (1) players are actually "more injured" in the general sense, (2) teams are reporting more injuries, (3) injury information is more available now than it was a decade ago, and (4) the AGL method needs an update similar to how Aaron revamps DVOA every so often due to changes in the nature of the game.

One thing we can say right now with confidence is that, as far as weekly injury reports go, teams do appear to be listing more players, and the increase can be seen among both starters and reserves. Specifically, if we look at the total number of injury listings in our database, we find that 2011 (4,357) had over 500 more than in 2008 (3,755) and over 1,000 more than in 2002 (3,317).

What's more, the past three seasons suggest that teams might be engaging in a bit of what I'll call "probable dumping:" After averaging about 1,300 probable listings from 2002 to 2008, the league has averaged a shade under 2,000 since 2009. Whether you think that's due to being conservative with injuries (a la Bill Polian) or playing shenanigans with reports (a la Bill Belichick) depends on your level of dispositional cynicism. We'll remain agnostic for the time being.

A second important trend is that year-to-year AGL correlations for each team have been much higher over the past three seasons than in the prior seven. Take the Seahawks, for instance. Their AGL has gone from 78.4 (ranked 28th) in 2008 to 75.2 (27th) in 2009 to 61.5 (24th) in 2010 to 78.6 (27th) in 2011. To be sure, we're still not seeing this sunrise-esque level of consistency across all teams, so the year-to-year correlation across the league isn't massive (in the 0.30 range). Nevertheless, that's a difference from 2000-2008, when the year-to-year correlation was .09.

The final leaguewide trend, and perhaps the one that's most definitive, is that NFL teams have officially completed their 10-year plan to eliminate "doubtful" as an injury listing worthy of public consumption. Recall that the way injury reports are supposed to work is that "probable" means a 75 percent chance of that player participating in the upcoming game, "questionable" means a 50 percent chance of playing, and "doubtful" means a 25 percent chance of playing.

It's been known for years that those guidelines aren't anywhere near what teams actually follow. That said, take a look at the graph below, which shows game participation rates for both starters (complete lines) and reserves (dotted lines) based on whether the players were listed as probable (green), questionable (amber), or doubtful (red).

There appear to be two clear ways doubtful is different from probable and questionable. First, whereas reserves play far less often than starters when they're listed as probable or questionable, there's basically no difference between the two groups in playing frequency when doubtful.

Second, and more importantly, the rate at which probable and questionable players actually play has remained level over the past decade. In contrast, doubtful players have gone from playing about 15 percent of the time in 2002 to playing only about 1 percent of the time in 2011. Furthermore, it's basically been that way since 2007.

The important point here isn't so much that the doubtful rate diverges from the league guideline. We can say the same about the probable rate, and -- again -- everyone knows this already. Rather, it's that shenanigans in the context of doubtful have increased over time, and to such an extent that the doubtful listing is completely meaningless.

So, to recap, what our injury data shows is that coaches have been "probable dumping" the past three years, and have been undermining the value of doubtful with increasing fervor over the past 10.

With that out of the way, here are the 2011 AGL totals for every team:

Team 2011 AGL 2011 Rank 2010 AGL 2010 Rank BAL 18.8 1 50.9 15 PHI 21.9 2 70.1 27 NO 24.6 3 45.0 13 DET 28.0 4 51.0 16 NYJ 30.4 5 41.9 12 MIA 31.7 6 51.0 17 TEN 37.7 7 31.6 6 SF 38.4 8 27.4 4 ATL 48.6 9 16.1 3 MIN 48.8 10 55.4 20 HOU 50.1 11 55.2 19 TB 51.4 12 60.8 23 CIN 51.8 13 62.4 25 CHI 54.5 14 12.3 2 DEN 55.4 15 51.7 18 GB 58.7 16 86.3 30 Team 2011 AGL 2011 Rank 2010 AGL 2010 Rank PIT 60.5 17 49.9 14 DAL 62.5 18 31.8 7 KC 65.5 19 10.0 1 WAS 67.5 20 69.9 26 BUF 71.0 21 41.7 11 CLE 71.8 22 94.7 32 SD 72.6 23 39.6 10 JAC 73.4 24 37.6 8 OAK 78.0 25 30.5 5 NYG 78.3 26 58.1 22 SEA 78.6 27 61.5 24 IND 84.7 28 90.5 31 ARI 86.8 29 38.3 9 NE 97.5 30 72.5 28 CAR 109.2 31 75.0 29 STL 110.0 32 56.9 21

Let's start with a few teams -- other than Indianapolis -- that had their seasons short-circuited by injury.

With their 110.0 AGL, the 2011 St. Louis Rams became the second-most injured team since 2002. Only the 2009 Buffalo Bills had it worse off. And like those Bills, the main contribution to the 2011 Rams AGL came from their defensive backfield, where their top three cornerbacks -- four if you count early-camp casualty Jerome Murphy -- were already out for the year by Week 10.

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Also not helping matters were another year of carnage at wide receiver (29.0 AGL after 26.4 in 2010) and 5.7 AGL for Sam Bradford. With injuries affecting the (offensive and defensive) passing game this much, it's no wonder St. Louis went from the cusp of the playoffs to winning only two games.

The team that saw the largest absolute increase in AGL (from 10.0 to 65.5) was Kansas City, so it's no surprise they lost three more games last season than in 2010. The interesting thing about the Chiefs is that about 60 percent of their AGL came from only four (albeit vital) players: Matt Cassel, Jamaal Charles, Tony Moeaki, and Eric Berry. Otherwise, they were an incredibly healthy squad: If not for those four significant losses, they would have ranked third overall.

Moving on to teams that saw their win totals clearly benefit from increased health in 2011, we have the two playoff participants from the NFC North. Detroit went from a team ranked in the middle of the AGL pack in 2010 to one of the healthiest teams in the league last season. Most of that good fortune came at quarterback, where Matthew Stafford's newfound durability resulted in a full season's worth of improved AGL at the position.

Classifying Green Bay as a team helped by increased health seems a bit odd given that they were coming off a Super Bowl championship in 2010. But remember that they only won 10 games that year. The same way improved health can be the catalyst for a rise from mediocrity (as in Detroit), it can also play a role in a 10-6 team improving to 15-1. Healthy seasons from Jermichael Finley and Ryan Grant dropped AGL at tight end and running back from 26.6 to 1.3, which likely contributed to a 24.5% improvement in offensive DVOA.

There were also a couple of teams that enjoyed relatively healthy seasons, but failed to capitalize on their good fortune. The New York Jets finished 2011 as one of the five least injured teams in the league, ranking seven spots higher than they did in 2010, but they lost three more games and dropped from sixth to ninth in total DVOA.

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The Jets have nothing on the 2011 Philadelphia Eagles, though. Despite having 48.2 fewer AGL than they did in 2010, ranking 25 spots higher in team health, the Eagles lost two more games, and missed the playoffs. It's true that Michael Vick had an assortment of injuries in 2011, but it turned out that he only contributed 0.2 AGL more last season than he did in 2010 (mostly because of differences in game status). Elsewhere, Philadelphia's offensive line AGL dropped by a full season's worth of games in 2011, as did their total AGL on defense. Taking their lack of injuries into account, calling the Eagles a disappointment last season might be understating it.

Finally, two teams in 2011 were what you might call the Bizarro Eagles: teams that found a ton of success despite ranking among the most injured in the league. You might also call them "last year's Super Bowl participants." Both the New York Giants and New England Patriots ranked in the bottom quartile of total AGL, and both saw their defenses decimated by injury over the course of the season.

For New England, almost half of their 57.6 AGL on defense came in the secondary (27.6), which is bad news for a team that has five or more defensive backs on the field over 60 percent of the time. For New York, last year's injury headlines were about the secondary and defensive line, but the largest AGL contribution on defense was from linebackers (23.4 out of 53.2). By the time Super Bowl XLVI came around, the Giants were down to their fourth-string middle linebacker, Chase Blackburn, who ironically ended up making the signature defensive play of the game.

Although the Patriots and Giants certainly deserve credit for successfully overcoming injuries last season, these weren't unprecedented feats by any means. In fact, last season marked the third year in a row -- and sixth time in the last nine years -- that the Super Bowl champion ranked in the bottom quartile of total AGL. It was also the third time in six years that both participants ranked 25th or lower.

Clearly then, as much as we talk about the importance of staying healthy, last year's Giants and Patriots showed us that doing so isn't necessary for a Super Bowl run. I guess you could say that last year's Eagles showed us that too, but not in a good way.

Next week, I'll profile the most- and least-injured team units from last season. Hint: The two most-injured units weren't even mentioned in today's article.