Given the historical success of undrafted quarterbacks in the NFL, Tony Romo might as well be a national treasure. We look at the impact of developmental leagues on undrafted quarterbacks, and just how many players have tried to break through in a recent season.
16 May 2011
by Aaron Schatz
I was intrigued by this John Clayton story from Friday in which Jim Schwartz suggests that the Lions drafted Mikel Leshoure because they want to use different kinds of running backs against different kinds of defenses. "You play 3-4 teams that are two-gapping," says Schwartz, "You need a big back who can run through some arm tackles. You want to get guys matched up on different teams, you need guys who can match up and beat linebackers and people that want to play man and trick coverage up for a certain player."
Clayton extrapolates this idea to a more general point: That smaller running backs are struggling with the rise of 3-4 defenses around the league. Is this true? I decided to give it a look -- albeit a quick, dirty, imperfect look.
I took all the running backs in 2010 who gained at least 750 yards on the ground and split them into two groups: larger backs and smaller backs. The split took place at 30.3 BMI, although I split the two backs with 30.3 BMI: Knowshon Moreno, at 5-foot-11 and 217 pounds, went into the "larger backs" category, while Ray Rice, at 5-foot-8 and 199 pounds, went into the "smaller backs" category.
I then looked at each back's performance against both 3-4 and 4-3 defenses. (I didn't count games against Buffalo, which switched back and forth and couldn't quite figure out what it was doing on defense last year.) I looked at yards per carry and DVOA, but also at broken tackles, because Clayton specifically noted the idea that you need a larger back to beat 3-4 defenses because they need to be able to break arm tackles. Our broken tackles numbers represent a number of different plays -- a broken arm tackle, a broken ankle tackle, juking the defender out of his shoes -- but I figured the results might be interesting.
Here are the averages for each group against the 3-4 and then against the 4-3.
Looking at yards per carry, it doesn't look like larger backs do better than smaller backs against 3-4. But it does look like an advantage that smaller backs have compared to larger backs against 4-3 tends to be neutralized against 3-4. However, the DVOA ratings are basically the same for both sets of backs against 3-4 and 4-3, which suggests that the phenomenon Clayton describes may not exist. And broken tackle numbers suggest that, on average, smaller backs actually break more tackles against 3-4 defenses than larger backs do.
Now, like I said, this is a quick-and-dirty study. A look at 25 backs in one season doesn't really disprove Clayton's thesis about different types of backs against different types of defenses. But the phenomenon certainly doesn't stand out with one quick look at the stats. Ironically, one back who really doesn't adhere to this thesis is the back Clayton uses as his biggest example: Adrian Peterson. Here is how Peterson performed against each type of defensive front in 2010:
Peterson didn't seem to have too much problem with the Packers defense last year -- 203 yards on 42 attempts -- and had big days against Arizona and Miami. He had his worst running day of the year against the 4-3 Giants. Clayton says that Peterson is the league's best at breaking arm tackles, and that he's struggled against 3-4 defenses in recent seasons. The two ideas don't seem to go together, and last year's numbers suggest that the former is more true than the latter.
I should note that I'm clearly working with some old player measurements that need to be updated -- for example, my files have Ray Rice listed at 199 pounds, while Pro-Football-Reference has him at 195 pounds and Clayton lists him at 212 pounds. (There's definitely an issue with figuring out how to handle changing weights of players in our many databases.) So Rice's current BMI probably should land him in the "larger backs" category, but he's listed in the "smaller backs" category. It makes some sense, since that's how Clayton mentions him in the piece. In addition, I also did a version of this study splitting the running backs who by weight rather than BMI (with the line drawn at 218 pounds) and the results were similar. That study would put Maurice-Jones Drew, Frank Gore, Knowshon Moreno, and Rice in the smaller category, with Steven Jackson and Arian Foster in the larger category.
For those curious, here are the numbers for all the backs in the study:
|LARGER BACKS||vs. 3-4||vs. 4-3|
|SMALLER BACKS||vs. 3-4||vs. 4-3|
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