Age and Defensive Performance

A quick post today...

Today we take on two pieces of conventional wisdom about how age affects defensive performance.

Conventional Wisdom #1: While you want veteran leadership, you don't wasn't a defense to be too old. After all, older players will get injured, and they get worn out by the end of the season.

The truth: Actually, there is a very strong correlation between age and a defense's performance. Namely, the older the defensive unit, the better the defense performs over the course of the entire season. This truth holds even when taking injuries into account. In fact, there is no relationship between how old a defensive player is and how many games he will miss in a season due to injury.

NFL defensive schemes are a complex thing to learn, and some gray hairs among the defensive unit are clearly a good thing, not a bad thing. So, if your team had upgraded on defense but you worry about the new acquisition's age, relax. The odds are likely that he will do more good than harm.

Conventional Wisdom #2: Penalties are a killer, and younger, less disciplined players are more likely to commit them.

The truth: Well, for starters, defensive penalties are not a killer. There is no relationship between the amount of penalties a defense commits and its defensive ranking. Nor is there a relationship between defensive penalties and the amount of points a defense allows. While a penalty in any particular game can obviously change the course of a game, over the course of a season, a defense will not be harmed if it is prone to penalties.

The second point to make about this addresses age and penalties. You often hear commentators calling penalties, "rookie mistakes." You also hear them mention how as a player matures, he will smarten up and stop making so many penalties. Well, according to statistics, this is nonsense. When it comes to committing a lot of penalties, it appears that players are who they are. There is zero statistical decline in a player's penalty rate as his career progresses. Furthermore, there is no relationship between years of NFL experience and the amount of penalties that a player gets.