Surprisingly, until the late 1990s little progress was made in determining how to evaluate the effectiveness of fielders and the relative importance of fielding (as compared to batting and hitting). Until recently the prevailing wisdom in baseball was that you had to have “strength up the middle” (good fielding at second base, shortstop, catcher, and center field) to have a good team. We will see that in most cases, the differences in player fielding abilities are not significant enough to be a major factor in team per for mance. As the saying goes, the exception proves the rule and we will see that the 2005 Yankees were a very poor fielding team, and we can estimate that their poor fielding cost them approximately eleven wins.
Fatally Flawed Metric
In our discussion of fielding, we will focus primarily on the important position of shortstop (SS). Until recently, the only measure of fielding effectiveness available was Fielding Percentage. For any fielder,
PO = putouts made by the fielder. For example, a SS gets credit for a putout when he catches a fly ball or line drive, tags a runner out, or receives the ball and steps on second base to complete a force out.
A = assists made by the fielder. For example, a SS gets credit for an assist when he throws to first base and the batter is put out.
E = errors made by the fielder. Again, whether a batted ball is scored an error is a subjective decision made by the official scorer.