BABIP

BABIP, or batting average on balls put into play, is a baseball statistic based on the research of Voros McCracken and others. BABIP measures a pitcher's average on batted balls ending a plate appearance, excluding home runs. It is roughly calculated as (hits minus home runs) divided by (at bats minus home runs minus strikeouts), at least as far as batters are concerned.

According to Baseball Prospectus, "BABIP is mostly a function of a pitcher's defense and luck rather than skill. Thus, pitchers with abnormally high or low BABIPs are good bets to see their performances regress to the mean." BP states that a typical BABIP for pitchers is about .290.

BABIP has also been applied to batters, but as batters have better control of where a batted ball goes (being the last actor), the appication is not as stark.