List of Major League Baseball single-inning strikeout leaders
In baseball, a strikeout occurs when a pitcher throws three strikes to a batter during his time at bat. Under Rules 6.05 and 6.09 of the Official Rules of Major League Baseball, a batter becomes a runner when a third strike is not caught by the catcher with no runner on first base or when there are two outs. The strikeout is recorded, but the batter-runner must be tagged or forced out in order for the defensive team to register the out. Thus, it is possible for a pitcher to  record more than three strikeouts in an inning. As a result of this rule, 90 different pitchers have struck out four batters in a half-inning of a Major League Baseball (MLB) game, the most recent being Domingo Germán of the New York Yankees on July 25, 2021. Four players — Chuck Finley, A. J. Burnett, Zack Greinke, and Craig Kimbrel — have accomplished the feat more than once in their career; no player has ever struck out more than four batters in an inning. Ed Crane was the first player to strike out four batters in one inning, doing so in  the fifth inning for the New York Giants against the Chicago White Stockings on October 4, 1888. Out of the 90 pitchers who have accomplished the feat, 63 were right-handed and 21 were left-handed. Twenty-six of these players (including seventeen active pitchers) have played for only one major league team. Three pitchers—Bob Gibson, Walter Johnson and Phil Niekro—are also members of the 3,000 strikeout club. Finley is the only pitcher to achieve the feat on three separate occasions, as well as twice in a single season. Pete Richert struck out four batters in the third  inning of his first major league game, becoming the only player to attain the milestone in his debut. Orval Overall is the sole player to strike out four batters in one inning in the World Series. Of the 26 players eligible for the Baseball Hall of Fame who have struck out four batters in an inning, four have been elected and two were elected on the first ballot. Players are eligible for the Hall of Fame if they have played in at least 10 major league seasons, and have either been retired for five seasons or deceased for at least  six months. These requirements leave 26 players ineligible who are active, four who are living and have played in the past five seasons, and fourteen who did not play in 10 major league seasons. References. General Specific