In baseball, a pitcher has an arsenal of different pitchers to befuddle the batter. The most common are the fastball and curveball, but beyond those two staple pitches lay a plethora of different pitches suited for different situations. One such pitch is a slider, which is part fastball and part curveball. It can be difficult to throw a slider, but it can also be one of the most effective pitches for striking out a batter.
The movement of a slider resembles a fastball as it approaches home plate. Many batters will assume the pitch is a fastball, in fact, which makes them adjust their swing accordingly. However, at the last moment, the slider will break down and away from the batter, causing him to swing over the pitch or miss it in some other capacity. When pitchers throw a slider, the pitch does not move as slow as a curveball, though it has a similar motion; and it does not move as fast as a fastball, though it takes on the appearance of one as it approaches the plate. The slider does not break as severely as a curveball; the motion is much shorter.
It can be difficult as well as potentially dangerous to throw a slider, especially for young pitcher. The arm motion a pitcher will use to throw a slider resembles that of a fastball, but the ball is held off center, usually while applying pressure against the ball with the middle finger. Throwing the pitch puts stress on the wrist and elbow, as the arm must whip in a similar fashion to a curveball motion, though not as severe. This motion can lead to arm injury in the elbow, wrist and shoulder, and therefore only developed pitchers should throw a slider.
The rotation of the ball when pitchers throw a slider causes it to drop down and away from the batter. This usually results in a pop-up or weak ground ball, as the batter is caught off guard by the late motion of the slider. When batters have two strikes against them, it is not uncommon to see an off-speed pitch come at them, like a curve ball or a change-up. The slider, however, is unique in that it appears to be a fastball until it’s too late for the batter to adjust; therefore, pitchers will often throw a slider when the batter has two strikes against him.