Football Injuries: The Metric That Matters

It’s football season in America again. Hallelujah.
As bad as most prognosticators are about most things, football prognosticators are really bad. Go back and look at just about any group of experts’ predictions for the coming season and you’ll see that their success rate is lower than that of the average monkey with a dartboard.
But for anyone looking to vindicate their terrible predictions, help has arrived: this article by Bill Barnwell of FootballOutsiders.com. It is a great look at a long-overlooked topic: the importance of injury on a given football team’s win-loss record. Using a metric called History-Adjusted Games Lost, Barnwell gives us an empirical look at the impact of various injuries on a team and a variety of nuances. If you are at all interested in the topic, you should read the entire article, but here are a few of Barnwell’s important conclusions:

• “Injuries, or their absence, have a drastic effect on a team’s success.”
• “A superstar is worth about six to seven times as much as a reserve.”
• “Offensive injuries are more significant than defensive ones.”
• “Injuries to the starting halfback do not affect the running game.”

So how do these conclusions help the case of bad football prognosticators?
Because football injuries are mostly the result of bad luck. Yes, you could argue that better players get injured less because they’re better prepared, better conditioned, and less likely to be caught out of position. But my sense is that these arguments may hold truer in a sport like baseball or soccer than in football, which is a game of collisions. If you agree that injuries are mostly the result of luck, then you could argue that many predictions go astray because the predictors couldn’t foresee the bad luck coming — but that their picks are otherwise sound.
If you run a football team and buy Barnwell’s analysis, then you’d probably want to spend a lot more time thinking about how injuries affect your season. Statheads have long grumbled that football has been slow to embrace a Sabermetric approach to the game (see Bill James here, on baseball; see Mike Zarren here, on basketball). It seems that football executives and coaches haven’t yet been convinced that certain statistical analyses provide the appropriate value and insight. But I can see how the kind of insights on injury that Barnwell offers might start to turn that tide. Even if a particular injury is the result of nothing more than bad luck, there are still lots of questions to empirically explore, such as:

• What is the optimal approach for a coaching and training staff to minimize injuries?
• What is the proper tradeoff between having very good and more expensive backups (an insurance policy against key injuries) and splurging for superstar starters?
• What is the best way to assess how a player’s previous injuries hurt his future abilities?

C’mon, NFL owners. There are a lot of newly minted statisticians out there. Surely a few of them are football fans who’d probably work cheap for a chance to bring some injury science to your business.