What is this? A Statcast metric designed to use data to evaluate the performance of baserunners and outfielders in taking or preventing extra bases.
How this works: Based on inputs including runner speed, outfielder throwing arm, runner position on the base paths, and outfielder distance from both ball and bases, an estimated success probability can be created for each opportunity. With that information available for each play, the player’s actual success rate can be compared to the estimated rate and the cumulative metric can be created, accounting both for bases taken (prevented, for outfielders) and chances taken or not. This does account for extra bases taken by batters or runners on batted balls; it does not include stolen bases, as it’s about taking extra bases against fielders. (Read more about this here.)
How to read it: “From 2020-’22, Trea Turner added 9 extra runs on the base paths, the most in baseball. In that time, Michael A. Taylor prevented 13 extra runs from baserunners, the most of any outfielder.”