Page "Designated hitter" Paragraph 70

In college baseball, NCAA rules state that the designated hitter must hit for the pitcher, but in many instances the pitcher is also a good hitter, and the coach may elect to let the pitcher bat in the lineup.

If the pitcher opts to bat for himself, he is treated as two separate positions — a pitcher and a designated hitter ( abbreviated P / DH on the lineup card ) — and may be substituted for as such ( i. e. if he is removed as the pitcher, he may remain as the designated hitter and vice versa ).

However, if a player who starts a game as a P / DH is relieved as the starting pitcher, he may not return to the mound even if he remains in the game as the DH, and he may not play any other defensive position after being relieved as the pitcher.

Conversely, a player who begins the game as the DH, but not as the pitcher, may come into the game as a reliever and remain as the DH ( in effect becoming a P / DH ), be relieved on the mound later in the game but continue to bat as the DH.