the key ideas underlying AGL (adjusted games lost) 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.
...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.
...which may mean that we may need to rely on the rookies and 2nd year guys more this year, if our lucky streak with injuries reverts back to even the 2010 level.