Split-finger fastball

A split-finger fastball or splitter is a pitch in baseball derived from the forkball. It is named after the technique of putting the index and middle finger on different sides of the ball, or "splitting" them. When thrown hard, it appears to be a fastball to the batter, but appears to the batter and observers to suddenly "drop off the table" towards home plate—that is, it appears to suddenly move downwards, towards the batter's knees. Despite the use of the word fastball, it is used as an off-speed pitch.

The splitter grew out of a much older pitch known as the forkball which was used in the major leagues since the 1920s. The modern splitter is often credited to baseball coach Fred Martin who threw the pitch in the minor leagues as a changeup of sorts. When a young Bruce Sutter returned from surgery to find his fastball had lost velocity, Martin taught Sutter the pitch. Sutter's success as a closer helped popularize the pitch.

Another early proponent of the splitter was Roger Craig, a pitcher-turned-manager in the 1980s. He taught it to a number of pitchers on the teams he coached, the Detroit Tigers and San Francisco Giants. According to Mike Scioscia, the splitter was "the pitch of the '80s."

The splitter eventually lost popularity after concerns arose that extensive use of the pitch could rob pitchers of fastball speed. Several major league teams actively discourage pitching prospects from throwing or learning the pitch. In 2011, only 15 starting pitchers used it as part of their regular repertoire.

The split-finger grip is similar to the forkball grip, but the forkball is pushed further back between the fingers and is usually thrown with a wrist flip that makes it slower than the splitter. The split-finger is often recommended as an alternative to breaking pitches to young players because of its simplicity and the significantly reduced risk of injury.

As it is an off-speed pitch, the splitter is generally thrown slower than a pitcher's fastball. According to PITCHf/x, the average four-seam fastball from a right-handed pitcher in 2010 was 92 mph, while the average splitter was 85 mph and the average changeup 83 mph.

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