In baseball, a strikeout occurs when a pitcher throws three strikes to a batter during his time at bat.
[3] As a result of this rule, 93 different pitchers have struck out four batters in a half-inning of a Major League Baseball (MLB) game, the most recent being Tyler Glasnow of the Tampa Bay Rays on July 7, 2023.
Five players – Chuck Finley, A. J. Burnett, Zack Greinke, Craig Kimbrel, and Tyler Glasnow – have accomplished the feat more than once in their career (Finley is the only one to do it three times, and all three times were within a one-year span);[4] no player has ever struck out more than four batters in an inning.
[6] 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.
[8] Of the players eligible for the Baseball Hall of Fame who have struck out four batters in an inning, four have been elected: Don Drysdale, Bob Gibson, Walter Johnson, and Phil Niekro.