A changeup is a type of pitch in baseball. Other names include change-of-pace and simply change. The changeup is sometimes called an off-speed pitch, although that term can also be used simply to mean any pitch that is slower than a fastball. In the early 20th century, the changeup was called a "slow-ball".
The changeup is thrown with the same arm action as a fastball, but at a lower velocity due to the pitcher holding the ball in a special grip. This difference from what is expected by the arm action can confuse the batter into swinging the bat far too early and thus receiving a strike, or not swinging at all. In addition to the unexpectedly slow velocity, the changeup can also possess a significant amount of movement, which can bewilder the batter even further. The very best changeups utilize both deception and movement. Johan Santana is thought by many to currently have the most effective changeup in Major League Baseball.
As pitchers age, some learn to greatly extend their careers after losing speed on their fastballs by taking advantage of the differences in speed between an effective changeup and a fastball of any speed. One such pitcher is Trevor Hoffman, who is renowned for a devastating changeup combined with an average speed fastball.
There are several types of changeup, which are generated by using different grips on the ball during the pitch.
The most common type is the straight change. The ball is held with three fingers (instead of the usual two) and closer to the palm, to kill some of the speed generated by the wrist and fingers. This pitch generally breaks downward slightly, though its motion does not differ greatly from a two-seam fastball. The Palm-Ball is a variation on this technique as well.
Another common grip is the circle change. The pitcher forms a circle with his index finger and thumb, using these two fingers to grip the seams of the baseball. This pitch tends to break slightly in the same direction as a screwball. Pedro Martinez has used this pitch throughout his career to great effect, and many consider it to be the future Hall of Famer's best pitch.
Another (less common) grip is known as the Vulcan change, where the pitcher wedges the ball between his middle finger and ring finger. Its name derives from the grip looking similar to the "Live long and prosper" hand gesture used by Vulcans, a fictional extraterrestrial race depicted on the television series Star Trek. This pitch's break resembles a forkball, going straight downward. Eric Gagne, a premier relief pitcher, utilizes this pitch extremely effectively.
In the past, many pitchers would throw the change by simply "taking something off" of their fastballs. Doing this can result in a different arm speed from the fastball, however, which may tip the hitter to the incoming changeup. Because the changeup is about deception and disrupting the batter's timing, today's pitchers almost always use some variation on the grips listed above, because they can be thrown with the same arm speed as a fastball, but with much slower results.