The NFL season is winding to a close, and while last week's games were great — and promise to be just as good this weekend — our focus, in large part, shifts to the offseason.
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One task on our offseason checklist is evaluating players. Why? Well, from March until early May, the NFL season's entire ethos is about player evaluation, valuation and acquisition. In my opinion, you can’t do the last two elements of that sequence well without the first.
However, football evaluation is hard. The samples are small, and the situations matter. For example, throwing passes from a clean pocket is different from a pressured one and running the football when the play is perfectly blocked is different than doing so when the play is not.
In this article, I want to look at linebacker play in the run game. I know, this isn’t the sexiest — or even the most valuable — part of football, but as teams continue to run the ball more than they should, linebackers who can stop the run have some importance.
Furthermore, errors of commission are huge in this area as well. You don’t want to overpay for something that is less valuable than you think and not measured properly (i.e. you’re not getting what you pay for).
We will look at how running backs perform in two subsets of data — plays that are perfectly blocked (as defined in this article) and ones that are not perfectly blocked.
In short, a perfectly-blocked run is when every offensive lineman performs their expected assignment (i.e. no one gets beat), whereas at least one offensive lineman is beaten on a not perfectly-blocked run. As you can imagine, plays that are perfectly blocked are really good for an offense. In addition, if there was a team that simply ran perfectly-blocked run plays, it would be the best offense in football:
Offensive efficiency metrics on perfectly-blocked and not-perfectly-blocked running plays.
From the linebacker's perspective, a perfectly-blocked run play means that no blocker is beaten in front of him — and even he might be blocked in such a manner that the offensive player is not downgraded. A not-perfectly-blocked run play means that someone (possibly the linebacker) is shedding a block and disrupting the play, and when the defensive line does so, it creates an easier play for someone at the second level.
The metric we are going to use here is “stops,” which we’ve charted for as long as we’ve had data. A stop is defined as a tackle (in this case in the run game) that coincides with an “unsuccessful” play — a play for less than or equal to four yards on first down, less than half of the remaining yards on second down, and short of the first down/touchdown on third and fourth down. This is mostly in line with what expected points added (EPA) says is an unsuccessful play but not perfectly.
Thus, we’re measuring a linebacker’s ability to make a positive defensive play with and without the help of the defenders in front of him. In many ways, this is similar to an analysis of a running back with and without the help of his offensive line, where we found that how a running back does on perfectly-blocked plays is noisier than how he does on not-perfectly-blocked plays.
We found that — much like for running backs — how a linebacker performs when the play is not perfectly blocked is more stable than when it is perfectly blocked: