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Trevon Diggs

Why Trevon Diggs hasn’t been the most valuable cornerback in 2021

By ALEX VIGDERMAN

Cowboys corner Trevon Diggs has been one of the most talked-about defensive players this season, starting with the opening game of the season in which he allowed one completion for 10 yards on four targets and picked off Tom Brady.

Since then, he’s followed that up with at least one interception in each game (with two in one of those games). That gives him twice as many interceptions (6) as anyone else in the NFL. He has the best total EPA on attempts as the primary defender in the league (-17 on 33 targets).

Despite all that, he’s not the leader among cornerbacks in Pass Coverage Points Saved.

Pass Coverage Points Saved Leaders, Cornerbacks, 2021

Cov Snaps Points Saved
Marshon Lattimore 174 24.8
Trevon Diggs 207 23.2
Asante Samuel Jr. 156 22.7

 

How is Diggs not the leader in Pass Coverage Total Points when he has six picks through five games?

To be honest, I would have expected him to lead because of that. Total Points gives defensive players credit for interceptions based on the EPA of the play, and interceptions are incredibly impactful from an EPA perspective. Diggs has accrued 23 Points Saved on those six plays alone.

Given that he only has 23 Pass Coverage Points Saved in total, that means that he has been roughly replacement-level on the plays where he doesn’t end up with the ball in his hands.

Given that he only has 23 Pass Coverage Points Saved in total, that means that he has been roughly replacement-level on the plays where he doesn’t end up with the ball in his hands.

Diggs is a bit hampered statistically by the fact that he’s covering top guys every week. He’s been targeted 33 times, third-most among cornerbacks in 2021. He has allowed a relatively high yards per coverage snap (1.4) because not only has he been targeted a lot, but receivers under his purview have been pretty successful overall (8.9 yards per target).

You could squint and see Jalen Ramsey of recent vintage—a quality defender who is put into spots that make it hard for him to maintain a good statistical profile. But it’s also a guy who has flashed every week with a big play that will outshine the rest of his performance.

That’s all well and good, but that doesn’t explain how a guy with many fewer interceptions (Lattimore) is able to jump him.

The biggest reason is that Lattimore has been targeted about as frequently as Diggs, but he has been much more successful in preventing completions overall. Lattimore’s Deserved Catch Rate—the percentage of catchable passes that the receiver either caught or dropped—is 48%, best in the NFL. As a part of that, he leads the league with nine passes defensed. Diggs, by way of comparison, sits at 76%.

Perhaps as relevant is that Total Points, as an EPA-based metric, gives players a lot of credit for performing on money downs. Lattimore has been targeted 12 times on 3rd and 4th downs so far, allowing just two completions and producing his one interception and eight of his nine defensed passes. At a team level, those 12 plays cost the offense 19 Expected Points.

 

I wouldn’t want to talk about the best cornerbacks of 2021 without also giving Asante Samuel Jr. some love, even if he’s a fairly convincing third place so far.

He’s been good on third and fourth down—but not as good as Lattimore.

He’s intercepted two passes—obviously much fewer than Diggs.

He’s allowed a Deserved Catch Rate of 82%, worse than either of the other two.

But what he has done very successfully is limit big plays against him. Of the 13 plays where any of these three has cost themselves at least one Point Saved, Samuel owns only two of them. He’s allowed three fewer yards after the catch per reception than Diggs with a comparable average depth of target (and if you’re worried, none of them has an outlier 70-YAC play skewing the average).

Samuel does have the lowest average depth of target against him of the three. Total Points accounts for that by evaluating the primary pass defender against the expectation of that play given factors like the throw location and coverage scheme. So he’s being judged relative to the job he’s being asked to perform.

The point of this isn’t to say that Diggs has had a bad season. Far from it. But just like referring to a quarterback’s TD:INT ratio only describes a small percentage of his throws, citing Diggs’ crazy interception numbers doesn’t tell the whole story, and other guys deserve to be discussed in the same breath as him through the first quarter-ish of the season.

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