Relief pitchers stand on the pitching mound, which is located in the center of the infield and 60 feet, six inches away from home plate.
Relief pitchers enter games after the starting pitcher has been removed, usually as a result of poor performance, high pitch count or injury. Many relievers work only an inning or two -- at most -- in a given game, though most clubs have a "long reliever" whose role is to come in to pitch two, three or four innings in relief of a starting pitcher who was removed from a game particularly early. The long reliever can also be useful in extra-inning contests, when the timeframe for a game's conclusion is uncertain.
Relievers typically throw harder than starting pitchers because they can afford to throw at maximum effort, knowing they are unlikely to throw more than 30 pitches in a day. But unlike their starting peers, relief pitchers can be asked to pitch on two or three consecutive days -- sometimes more -- though most relievers will require an off day after pitching three days in a row.
The handedness of a relief pitcher is critical. As a general rule, left-handed batters fare worse against left-handed pitchers, and right-handed batters will sometimes struggle against right-handed pitchers moreso than lefty hurlers. Inversely, a right-handed batter will often excel against left-handed pitchers, and left-handed batters typically perform best against right-handed pitchers.
Left-handed relievers, in particular, are often used in short stints due to their mastery over left-handed batters. Oftentimes, a left-handed reliever will enter a game to face just one left-handed opponent before being lifted for a right-handed reliever. Right-handed relievers are used in less specialized fashion, though such matchups are still an important component of managerial decisions.
On Offense: Relief pitchers very rarely come to the plate -- especially those in the American League, where the designated hitter is utilized. A National League long reliever will receive occasional at-bats if he enters a game exceptionally early, but many relievers will go an entire season without receiving even a single at-bat. Relief pitchers, like starting pitchers, are often asked to bunt if they come to the plate with a runner on first or second base and fewer than two outs.