The San Diego Chargers are 1-3 so far in 2007 and are on pace to win between only 3 to 4 games this year according to their efficiency stats. Their sole win has come against perhaps the only team considered more disappointing this year, the Chicago Bears. Media attention focuses on star running back LaDanian Tomlinson and his woes, but what are the real reasons for San Diego's slow start?
By comparing San Diego's stats in 2006 and 2007 through an efficiency model, we can see how the difference in each stat impacts the number of expected wins. The table below lists each efficiency stat in the model for both years. The column "+/-Wins" lists the estimated number of wins lost or gained due to the difference in each stat. Also listed is the Generic Win Probability (GWP) for the Chargers for 2006 and 2007. The GWP is the probability a team would beat the league-average team at a neutral site. The Adjusted GWP accounts for opponent strength.
|STAT||SD '06||SD '07||+/-Wins|
First, note that the Chargers were expected to win 12.3 wins last year, 1.7 wins short of their actual total. This indicates they were a solidly talented team, but there was some luck involved in getting to a 14-2 record. This year they are on pace to win 3.7 wins, a difference of 8.6 wins.
LT has seen his yards per rush attempt fall from 5.2 in 2006 to 3.4 in 2007, certainly a significant difference. But San Diego's running game only accounts for 1.6 of the 8.6 win difference between '06 and '07. Their passing game shares and equal amount of blame with a 1.6 win difference.
San Diego's opponents so far have an average GWP of 0.54, slightly above average. But this would only account for 0.03 in their own GWP so far. This equates to only 0.1 wins.
The Chargers' pass defense is the prime culprit, accounting for 3.4 wins of the 8.6 difference in expected wins. Last year their defense gave up only 5.36 yards per pass attempt, but this year they are allowing 7.39 yards per attempt (including sack yards). Although they've faced a ferocious New England passing attack and a resurgent Brett Favre, they've also played against below average QBs Rex Grossman and Damon Huard.
But in total, it's the Charger offense that's responsible for the bulk of their difficulties. Added together, their passing game and running game including turnovers are costing them 5.4 expected wins over the course of a season.
Are the Chargers a 4-win team? Maybe not. But for them to turn their season around, their pass defense needs to improve and not necessarily just their running game.