Although it was created to help assist in the objective evaluation of NFL prospects, the only thing the combine usually creates is confusion. With a variety of drills that have murky relationships to actual game-day activities, fans and scouts in the corner of a particular player can point to any positive performance as a sign of success. What does it mean that a defensive end had the eighth-best short shuttle time? Who cares if a tight end benched 225 pounds 25 times? Without context, they are just numbers.
So at Football Outsiders, we built in context. We've taken combine numbers and compared them to the future performance of those players to see whether they have any meaningful value in predicting success. No combine figure is ever going to be a foolproof indicator, but we have found that some drills are worth paying attention to at certain positions. And by making an adjustment to one drill -- the 40-yard dash -- for running backs, we came upon a metric that has a surprising level of relevance: Speed Score.
The concept behind Speed Score is simple: Not all 40 times are created equal. When a 225-pound player runs a 4.48 40-yard dash, it's a lot more impressive than that same 40 time from player who weighs 185. On top of that, the range of 40 times for running backs is so small (from about 4.2 seconds to 4.9 seconds) that even a miniscule difference can be valuable. Times of 4.41 and 4.51 might look like roughly similar, but in the NFL holes can close up just that quickly.