Defensive substitution
A defensive substitution in the game of baseball occurs when a currently non-playing player is placed into the field in place of another player, typically due either to injury or the appearance of a pinch hitter. In the American League, a pinch hitter is usually substituted for the position player in whose place he batted. In the National League, which does not use the designated hitter rule, pinch hitters sometimes bat for pitchers. However, another common pitcher-substitution strategy in the NL is the double switch, in which a pitching change is coupled with a pinch-hitter who is also defensively substituted for a second player.
