WAR Accumulation Differential: A Statistic for Identifying Undervalued Players

Recent emphasis on the wins above replacement (WAR) statistic in Major League Baseball (MLB) has been well documented. The benefit of classifying a player’s ability to generate wins beyond what a readily-available replacement player could provide has been useful in establishing the value of position players, pitchers, and hitters alike. Unfortunately, the statistic does not adequately address the efficiency with which players accumulate WAR, but rather the total value only. Players with limited playing time are thus penalized by the statistic. This paper presents a new suite of WAR-like statistics that measure the rate (or differential) by which WAR is accumulated. The new statistics are shown to be effective in highlighting valuable players who had limited playing time during the course of a season (e.g., young or injured players). In general, a properly normalized version of any cumulative statistic will have similar value.