Tuesday, October 5, 2010

Blind Side Project : How Good is D'Brickashaw Really

D'Brickashaw Ferguson is the left tackle for the New York Jets. He provides an interesting example to begin the ranking of offensive linemen because he has been in the league for four years, was the fourth pick in the 2006 draft, was selected to his first Pro Bowl last season after starting every game of his NFL career. Expectations for D'Brickashaw were high coming out of college and he appears to be realizing them. He also protects the blind side of a second year QB who many feel is below average and believe that his gaudy 8.5 adjusted yards per attempt and 0% interception rate is due more to short quick passes and loads of YAC than his true QB skill. This suggests that D'Brickashaw is not serving an insurance role as much as he is creating value for the Jets offense.

To get an idea of how effective a LT D'Brickashaw really is I used the data set that I have collected with the tremendous assistance of Keith Goldner. We now have 9 teams in the data set and enough pass attempts to make a first pass at evaluation. In order to evaluate linemen we will borrow from those that came before us at footballoutsiders.com (as well as many others) and compare performance to average. In this case though, what we are going to measure as performance, is the probability that, for a certain length of time, the lineman will be able to successfully hold their block.

Warning: Technical Stats Jargon in Use: Trying to estimate the average probability that a LT can hold a block for 2.5 seconds is tricky because the data is censored data. In this case, the phrase "censored data" means that on any play that a lineman holds his block successfully and the QB throws the ball after 2.5 seconds, we do not know how long the lineman could have held that block. The lineman may have been about to lose the battle, or maybe he could have continued to protect the QB for 2 or 3 more seconds...we will never know. This censoring of the data can lead to a biased estimate of the probability of success. Happily statisticians have built tools to deal with this problem, namely Cox Regression which is used in this first pass. Estimates are done by position.

Ok onto the results. Remember the linemen score reflects the  probability that the player adds or subtracts from the estimated average probability of success. The results below are for the Jets offensive line as this is the team that I have the most data for and thus the best estimates. I have also included a consistency score which is the standard deviation of a player's performance on a play-by-play basis (player predicted performance - average performance). Lower consistency scores mean the player is more consistent.

Player Ferguson Slauson Mangold Moore Woody
Grade 2.2% -1.8% 0.0% 2.0% -1.0%
Consistency 0.07 0.09 0.15 0.07 0.07

The 2.2% grade for D'Brickashaw is the highest of any linemen in the data set and his consistency score of 0.07 is tied for the best consistency score in the data set. Overall, the interpretation here is that Ferguson (LT) and Moore (RG) are consistently outstanding, Mangold's performance has been about average though highly variable and Slauson and Woody have performed well below average for their positions.

As the data set continues to get bigger, these estimates will be more precise and the effects will be more clear, and more teams and players will be ranked. This analysis as is though suggests that Sanchez gets Blind Side pressure on 2.2% fewer plays than the average QB. I think Jay Cutler is probably jealous.


  1. This is only taking into account the first 4 games of this season. So to rate Mangold as average is a little unfair considering he has played 2 1/2 of the 4 games hurt with a bad shoulder. Not to mention he is playing next to a guy who has basically no clue on passing downs in Slauson.

    I think if you graded out Mangold over a longer period, say last season for example, you would see he is the Jets best offensive lineman.

  2. "Sanchez gets Blind Side pressure on 2.2% fewer plays than the average QB. I think Jay Cutler is probably jealous. "

    2.2 percent or 2.2 percentage points?

  3. >2.2 percent or 2.2 percentage points?

    Whats the difference?

    I'll tell you, as a Jets fan, the first few game Ferguson did not perform well. Maybe you are rating him well because he "held" for 2.5 seconds but the ball was about to be thrown, and the "held" defensive player was about to sack the QB when he passed. He has been beaten on quite a few plays.