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How does Wins Above Replacement measure a baseball player’s value?

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Green retro manual baseball scoreboard beyond an empty, neatly mowed baseball field with brown infield dirt and striped grass outfield. — Sabermetrics A scoreboard provides some – but not necessarily the most useful – data on player and team performances in baseball.

Wins Above Replacement (WAR) is a sabermetric statistic designed to summarize a baseball player’s total contributions to their team in a single value for a given season. It accounts for a player's performance across all primary facets of the game, including hitting, fielding, base running, and pitching.1

The core principle of WAR is the identification of the value provided by a theoretical "replacement player"—a player who is readily available to a team from its bench or farm system. By comparing an individual player's production to this baseline level of performance, WAR estimates how many additional wins that player contributes to their team compared to what a replacement-level player would provide in their place. This metric evolved from earlier analytical methods, such as Bill James’s Win Shares and Pete Palmer’s Total Player Rating, and has since become a sophisticated tool for evaluating overall player value.1