Knuckleball

A knuckleball (or knuckler for short) is a baseball pitch thrown so as to minimize the spin of the ball in flight. The lack of spin creates a chaotic airflow over the stitched seams of the baseball and produces an erratic, unpredictable motion. This makes the pitch difficult for batters to hit, but also difficult for pitchers to control. The challenge also extends to the catcher who must make an attempt to catch the pitch, and the umpire who must determine whether it was a strike or a ball.

Grip and motion of knuckleball

As used by Cicotte, the knuckleball was originally thrown by holding the ball with the knuckles, hence the name of the pitch. Ed Summers, an Indianapolis teammate of Cicotte who adopted the pitch and helped develop it, modified this by holding the ball with his fingertips and using the thumb for balance. This grip can also include digging the fingernails into the surface of the ball. The fingertip grip is actually more commonly used today by pitchers who throw the knuckleball.

Related Topics:
Thumb - Fingernail

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Regardless of how the pitch is gripped, the purpose of the knuckleball is to avoid the rotational spin normally created by the act of throwing a ball. In the absence of this rotation, the ball's trajectory is significantly affected by variations in airflow caused by differences between the smooth surface of the ball and the stitching of its seams. The asymmetric drag that results will tend to deflect the trajectory toward the side with the stitches.

Related Topics:
Trajectory - Drag

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Over the distance from the pitcher's mound to home plate, the effect of these forces is that the knuckleball can "flutter", or actually curve in two opposite directions over its flight. A pitch thrown completely without spin is actually less desirable, however, than one with only a very slight spin (so that the ball completes perhaps between one-half and one rotation on its way from the pitcher to the batter). This will cause the position of the stitches, and therefore the drag that gives the ball its motion, to change somewhat as the ball travels, thus making its flight even more erratic.

Related Topics:
Pitcher's mound - Home plate

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A hazard of the knuckleball is evident in one sportscaster's desciption of the ball's behavior: "It either dances in or prances out." As a safety measure (for their earned run average) some pitchers will induce a slight topspin so that if no force causes the ball to dance it will move downward in flight. At the speed a knuckleball is thrown the batter is unlikely to swing and miss for a strike, but a slow ball that bounces is very difficult to hit and relatively easy for the catcher to block.

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