Steelers Now
Who is the best cornerback in the NFL right now? Where does Pittsburgh Steelers cornerback Joey Porter Jr. fall into that conversation? That’s, in many ways, a purely subjective idea, and it’s one that has stirred up a lot of debate this offseason. What’s best can have many forms.
The same is, of course, true, of offensive players. But offensive players have a statistical basis for their arguments. Who is the best wide receiver in the NFL right now? I might prefer Justin Jefferson, but it’s hard to argue with the statistical dominance of Jaxon Smith-Njigba, who led the league in receiving yards and tied for second in touchdowns.
There isn’t really a counting-stat corollary for defensive backs. The best possible defensive back play would result in no yards against. But if you sort the league’s cornerbacks by who allowed the least yards, you end up with a bunch of guys who barely played.
One of the recently developed defensive statistics, based on charting from coverage snaps like PFF, is passer rating when targeted. That gives a good breakdown of how successful quarterbacks are when targeting a specific defender, but it also has a huge blind spot. The best possible cornerback play results in no target most of the time. Just getting targeted is usually a sign that something has gone wrong for the defender.
There’s a statistic that’s been gaining steam on the offensive side of the ball called yards per route run. The basic idea is that the total yards don’t mean as much as the yards per opportunity.
Puka Nacua had 1,715 yards — well short of Smith-Njigba’s NFL lead. But Nacua played one fewer game. He ran 574 routes last season, while Smith-Njigba ran 582. In terms of yards per route run, Nacua was the more efficient player, 3.57 Y/RR, compared to 3.42 for JSN. They were first and second in the league, among players with at least 20 targets.
PFF does produce a similar statistic for defensive players — yards per coverage snap — though it doesn’t appear on their graphical consumer products. That does a much better of contextualizing the success of a defender than passer rating when targeted. But we can take that concept a step farther by borrowing from another offensive statistic.
One of my favorite metrics for evaluating the play of quarterbacks is adjusted net yards per attempt, or ANY/A. In addition to taking the average of the yards per attempt, it builds in the positive and negative contributions of splash plays. Each quarterback is credited 20 extra yards for throwing a touchdown and penalized 45 yards for throwing an interception, before the yards are divided.
We can do the same thing with cornerbacks, penalizing players for allowing touchdowns and taking penalties, crediting them for interceptions, and coming up with a better statistical picture of who was playing the best.
I’m calling this metric AYA/CS — adjusted yards allowed per coverage snap. If borrows the same interception and touchdown adjustments from...
