Using the PFR Play Index's Player Season Finder, you can run custom individual leaderboards across multiple seasons. For instance, here are the NFL leaders in Adjusted Yards per Attempt over the past three years:
As you can see, the leader (by far) is San Diego's Philip Rivers. In fact, 10th-ranked McNabb is closer to #2 Brees than Brees is to Rivers!
Statistically, it's tough to find a QB since 2008 who can touch Rivers. However, his team hasn't enjoyed the same lofty success: the Chargers are 24-16 over the past 3 years -- a respectable record, but one seemingly out of place next to Rivers' gaudy passing numbers. This disconnect between individual accomplishments and team performance has haunted many a quarterback in the past, and is now is the main reason Rivers isn't held up in the same group as Brady, Manning, Roethlisberger, and Brees as a quarterback. QBs are supposed to win, we're told, not amass seemingly empty stats.
But has Rivers really won that much less than we should have expected from his numbers? To answer this question, I went to the PFR Team Game Finder, sorted by passing yards, and collected every team game from 2008-2010. I calculated the Adjusted Yards per Attempt formula for each team game, and then ran a logistic regression between AY/A and whether the team won in a given game. The result of regression was the following equation, which tells us how often a team should expect to win based on their QB's AY/A in the game:
Win Probability ~ 1 / (1 + EXP(2.70534 - 0.412827*AY/A))
This means that if your QB posts a 6.55 AY/A in a game, you should expect to win half of the time; if he posts an AY/A of 9.22, you can expect to win 75% of the time.
To finish the study, I went to Rivers' game log page and ran the AY/A numbers on all of his 2008-10 games, calculating his expected winning % in each:
Adding up the expected win values of each game, we would have expected Rivers to win 27.7 of those 40 games, while in reality he won 24. Four extra wins in 2½ years can certainly make a big difference in playoff seedings, etc., but it's probably not as huge a difference as you might have expected, given that San Diego was a .600 team and Rivers has statistically been the top QB in the league by a wide margin. And even if San Diego's record did reflect Rivers' true ability, we would expect the QB of a .600 team to have an AY/A of 7.54, which still would have ranked 9th over the past 3 years.
The point is that while quarterback play is important, there are so many other areas of the game that can impact a team's W-L record. Winning 24 out of 40 games, like Rivers has, is actually what you'd expect from one of the league's elite quarterbacks. If you win more than that, it likely says a lot more about your teammates and coaching staff than anything you have done.
This entry was posted on Friday, November 5th, 2010 at 1:54 pm and is filed under PI Finds, Play Index, Quarterbacks, Statgeekery. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.