Measuring Defense

How important is defense? Anyone who follows the Twins found out over the weekend as the Twins defense implouded with Jose Offerman playing second base and the newly recalled Justin Morneau at first. The White Sox scored at least four runs they shouldn't have and that is being charitable to the Twins. With the exception of a few roto-rooters, most everyone agrees that defense is an important part of the game. The problem is measuring the contributions of individual players.

There are really two parts to this question. The first is the relative role of the pitcher and the fielders. The second is how we measure the fielders. Statheads are fond of the idea that pitchers have no control over how often a ball in play goes for a hit. According to this theory, it is entirely dependent on the fielders (or almost entirely, depending on the level of fanaticism of the proponent). Logically this has lead some people to measure team defense in terms of the team's batting average on balls in play. One Twins blogger over the weekend suggested this when looking at the batting average on balls in play of Twins pitchers this year. According to this theory, the 35 runs Twins pitchers gave up in their three losses could be attributed to poor fielding. At least every run not attributable to a walk or home run.

That theory seems to ignore the observation that those fielders were trying to catch some pretty hard hit balls. And If pitchers don't effect how hard a ball is hit - how are they responsible for home runs. This theory seems like the kind of wild-eyed nonsense that comes from staring at spreadsheets instead of watching baseball games. The fact is that pitchers do have an impact and the statistical data, not filtered through a preconceived ideological position, supports that. There is a reason Randy Johnson recently became the oldest pitcher to pitch a no-hitter, and it wasn't the Arizona Diamondback's defense.

So while defense plays a role in preventing hits - a role roto-players used to dismiss as unimportant - pitching is also an important component. This contributes to the difficulty of measuring the play of individual fielders. More on that tommorrow.