A screwball is a breaking ball designed to move in the opposite direction of just about every other breaking pitch. It is one of the rarest pitches thrown in baseball, mostly because of the tax it can put on a pitcher's arm. The movement on the screwball -- which travels toward the pitcher's arm side -- is caused by an extremely unorthodox throwing motion.
In throwing the screwball, the pitcher snaps his wrist in a manner that causes his palm to face away from his glove side. This is in stark contrast to sliders and curveballs, for which a pitcher snaps his wrist so that the palm is facing the glove side.
Because of the awkward arm motion, a screwball is exponentially tougher to throw than a curveball. But, in theory, it should have the same effect as a curve -- only breaking in the opposite direction.
Watch: John Smoltz demonstrates how to throw a screwball.
The origins of the screwball are very difficult to trace, as it was considered to simply be a different version of a curveball in its early years. Hall of Famer Carl Hubbell, who used the screwball to rejuvenate his career, brought notoriety to the pitch.
In A Call
"scroogie," "reverse curve"