A recent Pro Football Focus (PFF) tweet raised some eyebrows when it showed their top five running backs on the season through Week 10:
- Melvin Gordon
- Frank Gore
- Chris Carson
- Kareem Hunt
- Alvin Kamara
After looking over the reactions to the tweet, the chief objections were the absence of Todd Gurley and Saquon Barkley. Chris Carson’s rank at No. 3 placed him as the top-graded runner in the NFC, with both he and Alvin Kamara grading higher than Gurley and Barkley. With another running back in Carson’s own division receiving MVP consideration, has PFF lost its mind?
Actually, I think they have a good case, and the numbers back it up. Before you start yelling at your screen, please read to the end … and then yell if you’re still not convinced.
Efficiency: Gurley is King
Let’s start with the obvious: Gurley has been more efficient than Carson – and everyone else – on a per-carry basis. Through Week 10, Football Outsiders’ numbers put Gurley at No. 1 in success rate, DVOA (per-play efficiency), and DYAR (total value).
Case closed, right? Not so fast. We know that the Rams have the highest-graded run-blocking offensive line and that Gurley runs into light six-man fronts more often than any back in the league. Given this combination, we should expect his carries to be efficient.
Instead of saying that Gurley has been the most efficient runner in the league, we should say that the Rams have the most efficient rushing attack in the league. The question then becomes how to divide up the credit for Los Angeles’ efficient rushing offense, and there’s good reason to believe that the performance of running backs is team-dependent to a greater extent than other positions. We need look no further than the difference between Jeff Fisher-Gurley in 2016 and Sean McVay-Gurley in 2017 to see a compelling example.
Measurements of running back performance
Because team context – i.e., factors such as run blocking and box count – plays such a large role in determining rushing efficiency, it’s misleading to use a team’s rushing effectiveness to assess a running back’s performance. So what are we left with? Let’s go through a few measures that attempt to mitigate the role of team context.
Measure 1: Broken Tackles
Let’s start with the obvious: broken tackles. Any running back with adequate vision can run through a hole, but where running backs can separate themselves is their ability to break tackles.
Above is a plot of touches against broken tackles among running backs with at least 50 touches (all data are courtesy of SportRadar unless otherwise noted). More touches come with more broken-tackle opportunities, explaining the upward-sloping best-fit line. By measuring a player’s distance from the line (above = good; below = bad), we can create a ranking for the number of broken tackles a player has created above or below what would be expected based on his touches. Here’s how that looks among players with at least 100 touches:
This list aligns well with PFF grades, with the No. 1 graded player, Melvin Gordon, creating the most broken tackles above expectation. Coming in sixth – and third in the NFC behind Barkley and Adrian Peterson (!) – is Carson. Because Gurley lies below the best-fit line, his Broken Over Expected is actually negative, -1.4, ranking 20th among 34 running backs with 100 touches.
Another way to quantify broken tackles is how many touches a player would need to have before we’d expect him to break one tackle, on average. When looking at broken tackles in this way, Gordon is yet again No. 1, with a broken tackle every 6.7 touches. The top three in the NFC are a familiar group: Carson at the top (7.9), followed by Barkley (8.0) and Peterson (8.5).
A third way to measure broken tackles is to simply count the percent of time a running back goes down upon first being contacted. According to PFF, Carson is No. 2 in the league at avoiding being tackled at first contact. No. 1? You guessed it: Melvin Gordon.
Measure 2: Yards after contact
We’ve gone through a lot of ways of measuring broken-tackle rates, which, while informative, aren’t valuable in and of themselves. When a running back gets a carry, his goal is to gain yardage, not break tackles. So let’s turn to how a running back’s yards are created.
Below shows the top 10 running backs in terms of the percent of their yards that have been gained after initial contact among players with 100 rush attempts through Week 10:
I’m not sure much stock to put in this because of the problems with yards per carry (and especially given how one outlier could affect these numbers), but it’s an interesting list. There’s a lot of overlap with the above broken tackle list: Carson, Barkley, Hunt, Henry, and Gordon all appear on both lists. In addition, Gore makes an appearance, perhaps explaining his high PFF grade.
Another way to measure how a running back’s yards have been created is examining how many rushing yards they’ve gained after contact on the average carry. Again, we should take these numbers with a very healthy dose of skepticism, but the story they tell is consistent with the other measures we’ve seen. By now, I bet you can guess who the league leader is and who the NFC leader is. That’s right: Gordon (2.8 yards after contact per carry) and Carson (2.6), respectively.
Measure 3: Running back yards created
One of the biggest problems with relying on broken-tackle rates is that elusive runners can make a defender miss without getting credit for a broken tackle. Thus, our own Sam Gold has created a measure called running back yards contributed (RBc). While we don’t have numbers for every running back, here is how Carson and Gurley look:
The numbers above paint a similar picture to what we’ve been seeing. Gurley runs in an environment where more yards should be expected (higher offensive line contribution, in blue), regardless of who is running the ball, and Carson does more after accounting for what is blocked for him (higher RBc).
Receiving
The big caveat here is that we haven’t really talked about receiving. Since so much of a running back’s value in the modern NFL is in the receiving game, this is an important omission.
Does Gurley’s role as a receiver elevate him above Carson? I’m not so sure. While Gurley does have over 400 receiving yards while catching 76 percent of his targets, nearly 90 percent of his targets have come within five yards of the line of scrimmage, per nflscrapR. While Gurley is a better downfield receiver than Carson, I haven’t seen him being used much that way this year (for what it’s worth, PFF agrees: Gurley’s receiving grade is 15th among 22 running backs with at least 30 targets). A lot of Gurley’s big plays in the passing game in 2018 have looked like this:
The play design should get most of the credit here: When Gurley catches the ball, there are only two defenders outside of the left hash marks, leaving little for Gurley to do other than run into the end zone.
Finally, this has been an investigation into who has played the best this season, not who is the most valuable running back. If the discussion were about value, we’d need to shift our focus to someone featured prominently in the downfield passing game for reasons laid out here, likely landing on Kamara as the top back in the NFC.
Carson having a standout season
We’ve gone through a bunch of different measures attempting to isolate a running back’s performance from broader team context. While none of these measures tell the whole story, the picture they paint is remarkably consistent. Through Week 10, Chris Carson ranks in the top three in the NFC in the each following: Broken tackles over expected (No. 3), percent of yards after contact (No. 2), lowest percent tackled on first contact (No. 1), yards after contact per carry (No. 1), and PFF grade (No. 1). All of the evidence points in the same direction: It’s not crazy to call Carson at worst a top-three back in the conference, standing alongside generational talents in Adrian Peterson and Saquon Barkley.
(Top photo: Tim Fuller/USA Today)
