Before the universal DH (1973–2021)
The designated hitter rule was adopted by the American League (AL) in 1973, but the National League (NL) did not adopt it until 2022. During this period, the rules for pitchers depended on the league of the home team.
Pitcher batting: In National League parks and World Series games played at NL parks, pitchers were required to bat unless a pinch-hitter was used.
DH and substitutions: In American League parks, the designated hitter would bat in place of the pitcher. If a team used a DH, the pitcher was not in the batting lineup.
Loss of DH: An American League team would lose its DH for the rest of the game if the designated hitter was moved to a defensive position, or if a pitcher moved from the mound to another position on defense.
The "Ohtani rule" (2022–present)
In 2022, Major League Baseball adopted the universal designated hitter, standardizing the rule across both the American and National Leagues. At the same time, MLB created a new rule to accommodate two-way players like Shohei Ohtani.
New DH flexibility: A starting pitcher who also begins the game as the designated hitter can continue to bat as the DH even after they are removed from the game as a pitcher. This was a significant shift, as the previous rule would have forced the team to forfeit the DH position.
Purpose of the change: This new rule lets a two-way player contribute their offensive skills for the entire game without the team losing the DH when a relief pitcher is brought in. It only applies to the starting pitcher, not relief pitchers.
Practical effect: Now, a team with a two-way star can list that player on the lineup card as a "pitcher/designated hitter." Once the pitcher is relieved, the player simply remains in the game as the DH.
Examples of historic rulings
Early DH tests: The idea of a designated hitter dates back to the 1890s, when William Chase Temple proposed it, but it was voted down. It wasn't until a period of low offense in the 1960s that the idea gained serious traction again.
The phantom DH: In the early days of the DH, Orioles manager Earl Weaver exploited a loophole by listing a non-playing pitcher as the "phantom DH." This allowed him to use any available pinch-hitter later in the game. The league closed this loophole in 1980 by requiring the DH to bat at least once before being substituted.
Shohei Ohtani's early starts: Before the "Ohtani rule" was implemented, if Ohtani was pitching for the Angels, the team had to choose between letting him hit for himself or using a designated hitter. If they chose the former, they would lose the DH once he was replaced on the mound, a potential disadvantage. In 2021, on multiple occasions, Ohtani was listed in the starting lineup as a pitcher and a hitter, forcing his team to forgo the DH and giving them less offensive flexibility.