A screwball is a baseball and fastpitch softball pitch that is thrown so as to break in the opposite direction of a slider or curveball. Depending on the pitcher's arm angle, the ball may also have a sinking action.
Carl Hubbell was one of the most renowned screwball pitchers in the history of Major League Baseball. Hubbell was known as the "scroogie king" for his mastery of the pitch and the frequency with which he threw it. Other famous screwball artists include Tug McGraw and Cy Young Award winners Mike Cuellar, Fernando Valenzuela and Mike Marshall.
When thrown by a right-handed pitcher, a screwball breaks from left to right from the point of view of the pitcher; the pitch therefore moves down and in on a right-handed batter and down and away from a left-handed batter. When thrown by a left-handed pitcher, a screwball breaks from right to left, moving down and in on a left-handed batter and down and away from a right-handed batter. Due to this left-to-right movement of the ball (when thrown by a right-handed pitcher), right-handed pitchers use a screwball against left-handed batters in the same way that they use a slider against right-handed batters. If thrown correctly, the screwball breaks in the opposite direction of a curveball.
One of the first great screwball pitchers was Christy Mathewson, who pitched for the New York Giants 1900–1916, whose pitch was then labeled as the "fadeaway"; although historians have been unable to prove it, baseball legend holds that Giants manager John McGraw arranged for Black pitcher Rube Foster to teach Mathewson the screwball, as McGraw was forbidden from hiring Foster directly. Major league pitchers who have thrown the screwball during their careers include:
Contrary to popular belief, the screwball is not particularly stressful on a pitcher's arm. The pronation of the forearm allows for the protection of the ulnar collateral ligament, which is replaced during Tommy John surgery.