FALL 2022

AUTHORS

Ryan S. Brill, University of Pennsylvania
Justin Lipitz, University of Pennsylvania
Emma Segerman, University of Pennsylvania
Ezra Troy, University of Pennsylvania
Abraham J. Wyner, University of Pennsylvania

ABSTRACT

Traditional methods of computing WAR (wins above replacement) for pitchers are based on an invalid mathematical foundation. Consequently, these metrics, which produce reasonable values for many pitchers, can be substantially inaccurate for some. Specifically, Fangraphs and Baseball Reference compute a pitcher’s WAR as a function of his performance averaged over the entire season. This is wrong because not all runs allowed have the same impact in determining the outcome of a game: for instance, the difference in impact between allowing 1 run in a game instead of 0 is much greater than the difference in impact between allowing 6 runs in a game instead of 5. Hence we propose a new way to compute WAR for starting pitchers: Grid WAR (gWAR). The idea is to compute a starter’s gWAR for each of his individual games, and define a starter’s seasonal gWAR as the sum of the gWAR of each of his games. We find that gWAR highly values games in which a pitcher allows few runs (0 or 1).