Thursday, December 22, 2022

Comparing Individual Defensive Passer Ratings Across Two Platforms

 By Nick Webster 
There’s been a lot of focus on rookie cornerbacks this year, Derek Stingley Jr. and Sauce Gardner were picked 3rd and 4th overall, respectively in the 2022 NFL Draft, the first time in the Super Bowl era that two cornerbacks were picked in the top four overall. 

Fifth-rounder Tariq Woolen is tied for the league lead in interceptions with six and a series of other cornerbacks are making an early splash on the league at a position that typically takes a few years to work your way into.

Sauce Gardner, in particular, has garnered attention for his excellent early performance. He has a legitimate shot at being the first cornerback selected to be First-team All-Pro since Ronnie Lott in 1981. Interestingly, Lott trailed fellow rookie Everson Walls in interceptions that same season, Walls totaled 11, and Lott had “just” seven.  

Gardner isn’t gaining acclaim for his interception total but rather for his overall coverage skills and the fact that teams – including the Lions this last weekend - have just been avoiding him, he’s this season’s Nnamdi Asomugha.  

So, how do we rate these defenders if not by INTs, passer rating against is a good – if not perfect – way of evaluating Cornerbacks for their coverage skills.  And the Rookies this season are having excellent seasons. But by whose measure? We have two publicly available sources to compare individual defensive passer ratings - Pro Football Focus (PFF) and Sportsradar (SR), as published by Pro Football Reference.  

But charting pass coverage responsibility – unless you’re a coach – is an imperfect art.  I’ve tried myself, when a wideout is running free downfield is it a CB who’s responsible, or was it supposed to be passed off to a safety?  When two players bracket a wideout who’s primarily responsible? These are difficult to deal with.  

So how do PFF and SR compare in how they rate players? Let’s look at, season to date, Passer Rating Against stats for the starting CBs from PFF versus SR
What’s positive about this is that – in general – the two different services line up in their results.  They agree on the groups of the best the groups of the worst and the great big middle.  

But the single best and single worst defenders are not the same for the two services. The SR grades James Bradberry of the Eagles with a passer rating of 42.8 and PFF grades him at an amazing 45.7 – he’s been awesome in 2022.  

However, PFF believes that Jaycee Horn allowed a passer rating of just 39.4 – though SR graded him at just 55.0, which is still excellent. Now taking the average of the SR and PFF ratings #1 and #2 are still Bradberry and Horn and #3 is Sauce.

So where do the differences come from? For Horn, SR has him giving up one TD and PFF none, that’s the bulk of the difference. On Bradberry, they are very close at 45.7 (PFF) and 42.8 (SR).

What about Sauce? 
SIS has Sauce with 9 more targets and 10 more completions, this shows very clearly that there’s a difference in how each source applies responsibilities. Clearly, there are snaps that one applied to one and not the other.  If you drill down to the game level the differences become stark.

What are they doing differently mechanically?  Well, they don’t say, so we don’t know.  We do know that ¾ of the time the PFF passer rating allowed is higher and only ¼ SR is higher.  

It could be that SR has some concept of “blown coverage” that doesn’t apply blame anywhere, it could be that – given that I focused on cornerbacks – SR assigns more responsibilities to the safeties on long plays that go for TDs.

Finally, NFL Next Gen Stats also publishes coverage stats, but they don’t do so in a way that allows us to pull down chunks of data across players. They tend to assign responsibility based on who is closest in coverage using player tracking data. 

This is, at least, a systematic way of assigning coverage but would still fail in a blown coverage scenario where another defender comes to help, or in a double coverage scenario. What we know for sure is that the coaches know the answers and the public cannot get that data. We also know that, regardless of the source Bradberry, Horn and Gardner are having fantastic years and deserve recognition, interceptions aside.

1 comment:

  1. A huge difference between PFF and PFR this week vs Jax for Sauce:

    PFF: 1 comp on 2 targets for 23 yards (20 yac)
    PFR: 5 comp on 6 targets for 85 yards (50 yac)

    Will be interested to keep an eye on this for the last few weeks of the season.