In my column on injury rates [1] that I published yesterday on the Patriots Daily site, I promised that I would go over the effects by position in next week's column, the second part of the injury feature.
However, the column was almost immediately followed by Willie Parker breaking his fibula, not only costing my fantasy team its biggest weapon in its championship game, but according to some observers, the Steelers its season. With that in mind, I figured that it might make sense to discuss my injury research and what it says about running back injuries.
The good news for Steelers fans is that running back injuries don't show a significant correlation with many other variables -- at least, not relative to those injury rates at other positions. The relationship between running back injury rate and a team's wins from year-to-year was -.15; between RB injury rate and year-to-year DVOA, it was -.21. Both are middle of the pack as compared to other positions.
Correlation, of course, is not always causation, so let's try and drill down further into the places where running backs have a significant effect: Namely, let's focus on the offense. Here's where some of the more fascinating aspects of the research data can be teased out. As you would likely figure, there is some correlation between the injury rate of a running back and the difference in their year-to-year rushing DVOA, with a relationship of -.23. What's really interesting, though, is that quarterback injury rate enjoys a nearly similar relationship with year-to-year rushing DVOA, at -.21. What that implies is that losing a quarterback, on average, can be about as hurtful for a team's running game as losing the running back himself!
In the passing game, the reverse effect isn't as pronounced. The correlation between a quarterback's injury rate and a team's year-to-year passing DVOA is -.29; for running backs, it's only -.18.
Personally, I don't think the Steelers will miss a beat. Parker's not a particularly impressive back, and the workload he'd taken this year had seemed to sap some of his speed in recent weeks. His -11.5% DVOA [2] was nothing to write home about, while Najeh Davenport's DVOA is an immaculate 24.8%. Although he was ripping apart a very mediocre Rams defense tonight, Davenport's mix of size and strength has impressed onlookers, myself included, in the past. The only thing that's appeared to come between him and success has been playing time: He holds onto the ball (fumbling twice since 2003), he's a good pass blocker (he played fullback at Miami) and receiver, and although he runs a little high and sometimes seeks out contact instead of avoiding it, he's not a player the Steelers going to suddenly collapse with as their featured back. Oh, and he pooped in someone's closet once. But, hey, let he who is without sin cast the first... um... Najeh Davenport, everybody! Tip your waitresses.
Links:
[1] http://www.patriotsdaily.com/2007/12/outside-foxborough-the-injury-effect/
[2] http://www.footballoutsiders.com/stats/rb.php