Does Pitch Type - Zone Uncertainty Matter to a Pitcher's Performance?

Abstract

Baseball is a game of numbers. Large-scale baseball data have been utilized in decision making process by team managers. Recent studies with PITCHf/x, a system that tracks every pitch, provide new insights on the role of the pitch-type sequence in the pitcher’s performance. These studies are based on the assumption that the pitch-type uncertainty puts the hitter at a disadvantage. However, the pitch-zone uncertainty, another factor of pitching uncertainty, is neglected in many cases. Here, we introduce normalized mutual information for pitch type and pitch-zone as an indicator of pitching uncertainty. A pitcher with less of a repertoire with respect to type-zone combination has high normalized mutual information in pitching. We calculate the pitch type - zone uncertainties for major league baseball starting pitchers and compare the results with field independent pitching, a metric of pitcher’s performance. Our analysis shows that normalized mutual information is uncorrelated with performance in nine distinct subgroups extracted from revealed comparative advantage in pitch type. This result underlines the importance of the pitcher’s repertoire and ability to be competitive in professional baseball.