zWins, an Alternative Calculation of Wins Above Replacement in Baseball

Walter King, Undergraduate Student, The Ohio State University


Abstract: zWins is a new methodology for Wins Above Replacement (WAR) in baseball, which outperforms and overcomes weaknesses of existing WAR measures by introducing major innovations and providing a flexible system of calculations with complete disclosure of all formulas and methods. WAR is the most widely used measure of player productivity in baseball, and estimates how many additional wins each player produces relative to their presumed replacement. WAR is an attractive concept; it considers offense, defense, and pitching to give each player one number that represents their productivity measured by their direct effect on team success.
Improved measures of performance serve to better inform management decisions regarding player compensation, trades, and other features of player personnel. In Major League Baseball, where players regularly command economic investments on the magnitude of nine figures, it necessary for teams and owners to have accurate measures of player productivity to properly gauge the monetary value of players.
zWins improves upon not only WAR, but also the subcomponents that make up offensive and defensive estimates of performance. In particular, the run production model used in zWins is consistently more accurate than the production models used in various WAR measures, and provides a cohesive strategy for estimating the performance of pitchers and fielders. As a result, zWins shows superior accuracy over competing WAR measures when tested against both actual team performance and Pythagorean Expectation.

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