A changeup is one of the slowest pitches thrown in baseball, and it is predicated on deception.
The changeup is a common off-speed pitch, and almost every starting pitcher owns a changeup as part of his arsenal. (A larger number of relief pitchers do not, because they typically only face hitters once and therefore have less of a need for deception.) A good changeup will cause a hitter to start his swing well before the pitch arrives, resulting in either a swing and miss or very weak contact. But when a hitter is able to identify the changeup, the pitch is among the easiest to hit because of its low velocity.
There are several different grips that pitchers use for a changeup, but the common theme is that the ball rests farther back in the hand -- even, in some cases, in the palm. They are thrown with a nearly identical motion to that of a fastball, causing the intended deception.
Watch: John Smoltz demonstrates how to throw a changeup.
The changeup has been around for as long as the game has existed. In the early days of baseball, when breaking balls were considered unfair and deceitful, most pitchers settled for throwing exclusively straight pitches, and a few of them mixed speeds. Thus, the slower pitches in that era could be considered the game's first changeups.
In A Call
"change," "change of pace," "off-speed," "slowball," "the dreaded equalizer"