Defensive Most Valuable Player According to NFL Plus-Minus: Chris Jones

Using historical on-off the field splits and player clustering to estimate value of defenders

The NFL Honors ceremony was last night and all the seasonal awards were handed out to offensive and defensive players. The expected result came for Defensive Player of the Year (DPOY) when Nick Bosa’s name was called.

Bosa led the NFL with 18.5 sacks during the regular season, 2.5 more than Myles Garrett. (Hassan Reddick, who will be discussed later, now has 19.5 through the playoffs).

Bosa was ranked first for DPOY by all but one of the 50 voters, and the new rank ordering system had Bosa with more than twice as many voting points as the next closest defender Micah Parsons. The other players receiving first-place votes were Reddick, Quinnen Williams and Chris Jones.

In this post, I’m going to detail the methodology and results applying my NFL Plus/Minus metric to defenders this season, and every player mentioned above shows up as a top-12 most valuable player for 2022. However, the ordering differs somewhat significantly from the consensus opinion reflected in DPOY voting.

My NFL Plus/Minus methodology will evolve as time goes on, and the results will also change. Even so, the first run of results point to a few potential gaps in our current understanding of where defender value comes from, and points to one player as clearly the most valuable this season: Chiefs’ dominant interior defender Chris Jones.

Yesterday I detailed the NFL Plus/Minus methodology and results for all non-quarterback offensive players (showing that Tyreek Hill is probably not getting enough credit), and in this post we turn to defenders.

METHODOLOGY

Using participation data and on- and off-the-field splits have a rich history in other sports for building player valuation metrics. No matter how much we try, the human eye and brain cannot notice the contribution to every player on every play while calculating the exact impact of those actions on the game in a comparable metric. By studying the differences in team success — in this case, using expected points added — when a player is on and off the field, we can capture the entire effect in useful numbers for comparison. 

The issue with using on-off splits in football is the time for all players on the field is limited in a 17-game season, and the substitution patterns for different positions don’t allow for much comparison. Without injury, cornerbacks can play every snap of the game, whereas certain interior defenders are rotated consistently. The solution I came up with was to look at the on-off splits of groups of similar players rather than individual players.

I used the nflreadR participation data going back to 2016 — along with other traditional and advanced stats — to cluster similar players for each position in each facet of the game and then compiled the on-off splits of those groups. In doing so, we increase the total samples of measurement and reduce the noise of single-player numbers. 

Before we get into the results of the analysis for every defensive position, let’s walk through a specific example of how clustering works, using the coverage facet for cornerbacks.

Without getting bogged down in the details, the graph above divides all cornerback seasons with at least 25 coverage snaps from 2016 to 2021 into eight different color-coded clusters. The metrics used to group the clusters include coverage grade, percentage of snaps targeted and percentage of snaps in the slot. This is a simplified version of the actual clusters used in the analysis, which are more numerous and contain fewer players per cluster.

I’ve highlighted a handful of cornerback seasons from 2022, showing that young studs like Sauce Gardner and Patrick Surtain are in the direction of higher grading, and the opposite direction of higher yard and touchdown rate (per coverage snaps) where Greedy Williams resides. Mike Hilton is an example of a strong slot corner, which falls in the lower lefthand side. Mike Hughes wasn’t as strong in cover, and spent significant time in the slot. Jaire Alexandre wasn’t quite on the level of Gardner or Surtain in his grading, but 1% interception rate (per coverage snap) was the second highest for cornerbacks with at least 200 coverage snaps, pushing him upwards on the plot. Derek Stingley was roughly in the middle of the pack by most metrics in his rookie season.

Once we have players assigned in clusters, we total up the team-level expected points added with the clustered players on- and off-the-field then come up with a per-attempt number for the average value added by that cluster versus their teams giving coverage snaps to other cornerbacks.

Unsurprisingly, historical on-off splits show that teams miss cornerbacks like Gardner and Surtain when they’re off the field. Strong slot corners like Hilton also have a big effect, as is the case for the Alexander cluster.

For the NFL Plus/Minus results, this exercise of clustering by role is applied to every position in all three facets of defensive play: pass rush, run defense and coverage. The results below detail the points prevented (negative is good) numbers for the top-10 defenders in every position group and then the top-12 overall. I’ll post more commentary after on the results and how I’m thinking about them.

THE RESULTS

The tables below include the players’ overall points prevented in 2022, the per-game figure and the snap and points prevented for each facet of pass-rushing, run defense and coverage.