Relief pitcher

baseball or softball pitcher who relieves a previous pitcher

In baseball and softball, a relief pitcher or reliever is a pitcher who enters the game after the starting pitcher is removed. There are different kinds of relief pitchers such as closers, set-up relief pitchers, middle relief pitchers, left/right-handed specialists, and long relievers. Relief pitchers are expected to pitch many games but in fewer innings than starters.

A relief pitcher warming up in the bullpen.