Aboutt a month ago, I introduced a method for valuing offensive line play using advanced statistics. The full explanation can be found in the original post, but the basic concepts goes like this:
The offensive line's job is, ironically, defensive. Lineman protect the quarterback or the rusher from tacklers. The best an offensive line can do is prevent their opposition from making plays, either by hitting or sacking the QB, by tackling a rusher for a loss or short gain, or by deflecting a pass. The impact that an opposing front seven defenders make can be measured by their +EPA or +WPA. These stats count only plays in which the defense scores a 'victory' by forcing a setback on the offense. An offensive line can be measured by how few 'victories' they allow, measured by how little +EPA or +WPA they forfeit to their opposing front seven.
In this implementation, the +WPA/+EPA of opposing defensive lineman are counted for all plays, and the +WPA/+EPA of linebackers are counted in only runs and pass rushes. In other words, pass defense plays by linebackers are excluded because the offensive line has no influence on linebackers in pass defense roles.
For example, the Patriots' offensive line leads the league with opposing defensive front sevens totaling the least +EPA with 84.6. The league average allowed +EPA for offensive lines is 127.6. That makes the NE offensive line 43.0 EPA better than average.
The end result are stats I call Negative Win Probability Added (-WPA) and Negative Expected Points Added (-EPA). They are called negative because they measure the absence of opposition success.
Of course, quarterbacks and running backs would have an impact on this type of statistic. Just like in almost all other aspects of football, there is a clear interaction between the line and the backs' performance. But the reverse is true as well (offensive lines certainly affect QB and RB stats), and most people are happy to accept statistics that treat a passer's or runner's stats as their own. At the very least, we have some useful stats that can measure the impact on line play due to a change in QB or RB.
I've created a page devoted to offensive line statistics, updated weekly after each set of games, just like all the other stats here. You can even go back and look at offensive lines from previous seasons. There is -WPA and -EPA, plus each stat's run and pass components. I've also included some other more conventional stats such as sacks allowed, sack yards allowed, QB Hits, and Tackles for Losses Allowed.
But even for those more conventional stats, I've only included those sacks, hits, losses, etc. due to front seven defenders. The defensive backs are typically not the responsibility of offensive linemen. It's usually up to the running back to pick up a blitzing DB or up to the quarterback to look for the hot read.
One note: when two defenders are each credited with a sack or tackle for losses, my system counts that play as two sacks allowed or two tackles for losses allowed. This is because there were at least two failures in the offensive line on that play that led to the outcome.
New Offensive Line Page
By
Brian Burke
published on 11/29/2010
in
research
Subscribe to:
Post Comments (Atom)
How balanced is the official scoring for defensive counting stats "sacks, tackles, etc" these days? Years ago it was terribly skewed, with some teams ending up with nearly twice as many "tackles" per play as others over the course of a season.
If that's still the case you'll want to include some normalization in the analysis, check how a given O-Line performs against a D-7 relative to the other O-Lines that D-7 faces.
For some reason the new page does not seem to be loading.