In baseball, a middle reliever or middle relief pitcher, is a relief pitcher who typically pitches during the fifth, sixth, and seventh innings of a standard baseball game.[1] In leagues with no designated hitter, such as in the National League prior to 2022 and the Japanese Central League, a middle reliever often comes in after the starting pitcher has been pulled in favor of a pinch hitter. Middle relief pitchers are usually tasked to pitch one, two or three innings. Several factors determine this such as who’s currently winning, what the score is, eligible bullpen pitchers remaining, importance of the current game etc. After the middle relief pitcher has completed his portion, they are then normally replaced in later innings by a left/right-handed specialist, setup pitcher, and/or lastly a closer. When they’re replaced is in part due to deprivation of stamina and/or effectiveness but also characteristics such as pitch arsenal, speed of pitches, which arm they throw with and who’s up to bat next for the opposing team. Middle relievers may sometimes pitch in these later innings as well, especially during games that are tied or close in score.
. Paul Dickson (writer) . The Dickson Baseball Dictionary . 2009 . . 544 . 978-0-393-06681-4.