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Regular readers know that I am not a big fan of yards per carry to measure a running game, on either the team or the individual level. That also goes for team defense. If you look at this year’s standings, though, and compare a team’s record to its yards per carry allowed, you will in fact notice a correlation.

And a moderately strong one at that. The correlation coefficient between a team’s winning percentage in 2017 and that team’s yards per carry allowed is 0.37. That indicates a positive correlation between the two stats, but… well, there isn’t supposed to be a positive correlation. This means that allowing more yards per rush is correlated with winning more games. See for yourself:

The #1 rushing defense, as measured by yards per carry, belongs to the 0-13 Cleveland Browns. The #32 rushing defense, as measured by yards per carry, belongs to the 10-3 New England Patriots. The five worst rushing defenses all belong to winning teams that will almost certainly make the playoffs (with the exception of the Chargers, who just have a good chance to make the playoffs). The two best rush defenses, by far, belong to the Browns and Broncos.

Rushing and rush defense aren’t the most important elements of a team’s game, but they’re certainly not unimportant. Measuring them by yards per carry, though, is rarely a good idea.

  • The one that always gets me is how there’s virtually no correlation between penalties and winning. Looking at this year, the correlation coefficient between penalties and wins is 0.10 and between penalty yards and wins is -0.04. I suppose the good teams just know how to cheat properly.

    • Richie

      I suspect that the TYPE of penalty might make a difference. For instance, committing a lot of pass interferences could be an indicator of defenders who are doing a good job of being near the receiver and making plays on the ball. So even a good team might commit a lot of DPI.

      But, maybe things like illegal motion, offsides, false starts, are more mental errors that wouldn’t have any positive impact.

      • McGeorge

        I agree.
        Cutting back on false starts can really help, and making a lot of false starts is a killer, especially for weak offenses.
        And if Von Miller gets called for a few neutral zone infractions but also gets a strip sack its a good trade off.

        Maybe have 2 categories of penalties (Mental Errors (which include PF) and Other)

        • Richie

          Personal Fouls might even be beneficial as an intimidation factor.

          • McGeorge

            I don’t know. I see all kinds of dumb PF that just hurt the team. Most aren’t the intimidation kind.

            • Richie

              Yeah, you would probably need to categorize them. I think a personal foul, roughing the QB could be a sign of a strong pass rush that is getting to the QB, and could cause the QB to be nervous on future dropbacks. But on one of those plays where the guy just shoves the QB down a full second after the pass is thrown is just bone-headed.

              Here’s a website I recently discovered, if you like looking into penalties: http://www.nflpenalties.com/

              • McGeorge

                Oh Nice!
                Thank you for the link.

                Looking at von Miller, these seem like ‘Good’ penalties, that show aggression.

                Defensive Offside (7),
                Defensive Holding (1),
                Neutral Zone Infraction (1),
                Unsportsmanlike Conduct (1),
                Roughing the Passer (1)

                Looking at Austin Seferian-Jenkins (TE) the results look ‘Bad’

                Offensive Holding (5),
                Offensive Pass Interference (1),
                False Start (1)

      • Adam

        This is true. Football Outsiders counts procedural penalties against the offense because they’ve found that mental errors correlate with bad play overall. Yet they don’t count holding, illegal contact, personal fouls, etc, because those penalties often indicate an aggressive style that pays off in the long run.

        • McGeorge

          Doesn’t holding equate with – “You got beat”.
          Thats not due to aggression, its due to either bad play or being outmatched.

  • Joseph Holley

    Is this maybe because rushing is not as important to winning as passing is, at least in 21st century football? I would think that the coefficients would look different for the 70’s.
    This is another one where I am going to say that success rate matters. As a Saints fan, I have seen them stop runs in a lot of key short yardage situations this year. It shocks me to see their YPC be that high–although maybe b/c they are winning, teams pass against them more, so with fewer carries against, the bigger runs inflate the average more.
    Speaking of that, how much would the YPC for the Browns change if you removed kneel-downs against? I wonder if those 2 to 3 runs per game for negative yards might influence the average.

  • Dan

    It may be that the best coaching staffs have figured out that it makes sense to sell out on stopping the pass (e.g., by playing an extra DB) even though that means giving up more rushing yardage per carry. I’ve heard that this is what the Chargers have been doing.

  • Adam

    This is pretty crazy. Good find, Chase!

    I do think rushing success rate matters for both offense and defense, but that isn’t really captured by YPC. My guess is the positive correlation in 2017 is just randomness, and in prior years the correlation is close to zero.

    My other (slightly offbeat) theory is that a dominant run D can actually hurt the defense overall, especially in today’s NFL. Since passing is now far more efficient than running, offenses facing a stingy run D will throw the ball even more…which is what they should’ve been doing in the first place.

  • evo34

    “Predictive”?? I expect more from this great site. It’s a correlation — nothing else — and the causality is almost certainly the other way around. Trailing teams tend to not have short yardage to gain for first down and so will run rushing plays designed to gain more than two yards. Additionally, leading teams will tend to protect against the pass, allowing the occasional successful rush. In general, the more you run the ball, the harder it is to have a high YPC. Leading teams run the ball a lot, and trailing teams do not. Hope this solves the mystery…

    • McGeorge

      Thats what I was thinking too.

  • LightsOut85

    My initial reaction – at least for the best/worst teams, is that a poor team has opponents who are going to be doing more running to close out the game & the team-in-question knows it’s coming & “sells out” against it. Vice versa with the best teams, they’re expecting their opponent to pass to close the point-gap, and thus some longer runs are produced.