Do Running Backs See a "Verducci Effect"?

by Aaron Schatz

You may have noticed Will Carroll mention in his column today that, after considering the likely rise in carries that Maurice Jones-Drew will get this season, he asked me to research if there is some sort of "Verducci Effect" in football. For those who don't know, the "Verducci Effect" comes from Sports Illustrated's Tom Verducci, who noticed that pitchers who go far past their previous career high in innings pitched tend to have injury or decline issues the following season. So the question here is whether the same thing happens with part-time running backs who become high-workload full-time running backs. Is there an effect from increased workload, and is it anything like the effect of ultra-high workload that we call "The Curse of 370."

(As an aside, I know that some people have questioned the Curse of 370 recently. It was always meant to be a rough guideline, not a hard and fast rule -- it isn't as if 369 carries is "safe" and 372 carries automatically means "screwed" -- and I will add that I'm totally open to considering criticism as to why this theory may be flawed. However, the best way to make that criticism is not to leave discussion thread responses but rather to e-mail well-explained, constructive comments to info-at-footballoutsiders.com -- and the key word here is "constructive" as opposed to "indignant." Digression over.)

Don't consider this fully-vetted, 100-percent scientifically accurate research, but I did a quick-and-dirty search to look at backs with a major workload increase since 1978. First, we need a control group: Every running back since 1979 with at least 250 carries in a season. These running backs on average dropped the following year by 325 yards and .25 yards per carry. (The yardage average includes guys who retired or did not play the following year due to injury; the yards per carry average does not.)

Next, I looked at "workload increase" backs. This group included those who:

1) Carried the ball at least 250 times
2) Previously had a career high below 150 carries
3) Increased their workload by 200 or more carries compared to the previous season

This gives us 19 running backs, including Michael Turner. The other 18 running backs in the sample dropped the following year by an average of 230 yards and .26 yards per carry. The problem is that not all these backs are guys you would think of as "part-timer with sudden workload increase." Seven of them were in their second year -- those aren't part-timers, those are guys who weren't given a heavy workload as rookies, such as LenDale White and Shaun Alexander.

If we take out the second-year players, there does seem to be a small "increased workload effect." The remaining 11 players dropped the following year by an average of 368 yards and .38 yards per carry. Of course, you can't really go by such a small sample size, and part of the reason for the drop in yards per carry is that some of these guys were absurdly good in their "increased workload" year. After Larry Johnson averaged 5.2 yards per carry in 2005, would you blame "increased workload" for his drop to 4.3 yards per carry the next season? Or would you blame plain old regression to the mean, not to mention the deteriorating Kansas City line of that time?

I tried increasing the sample a little bit by looking at backs who:

1) Were in their third year or older
2) Carried the ball at least 225 times
3) Previously had a career high below 150 carries
4) Increased their workload by 150 or more carries compared to the previous season

Now our sample is back to 19 backs, including Michael Turner. The 18 other backs here dropped the following year by an average of 355 yards and .32 yards per carry. I put those backs in a table below for those curious.

Finally, let's compare these "increased workload" groups to the good ol' Curse of 370. Twenty-eight backs have gone over 370 carries during the regular season, including "Curse-Buster" Eric Dickerson four times. Those backs dropped in the following year by an average of 714 yards and .55 yards per carry -- a much larger drop.

Overall, I would say the difference is too thin and the sample size is too small to say that running backs with a massively increased workload are in particular danger -- unless, of course, that workload went up into the high 300s.