Designated hitter

The designated hitter (DH) is a baseball player who bats in place of the pitcher. Unlike other players in a team's lineup, they generally only play as an offensive player and usually do not play defense as a fielder or a pitcher during a game. Due to their specialized offensive-only role, the designated hitter is generally expected to produce above average offensive stats and production compared to other players who play defense.

In Major League Baseball, the position is authorized by Rule 5.11 of the Official Baseball Rules. It was adopted by the American League in 1973 and by the National League in 2022, making it universal in MLB. Within that time frame, nearly all amateur, collegiate, and professional leagues worldwide have adopted the designated hitter or some variant, except for Nippon Professional Baseball's Central League.

The designated hitter is a player who does not play a position in the field, but instead replaces the pitcher in the batting order. However, a starting pitcher (but not relievers) may choose to also start as the designated hitter so that the pitcher bats for himself. The DH may only be used for the pitcher (and not any other position player) as stated in Rule 5.11. Use of the DH is optional, but must be determined before the start of the game. If a team does not begin a game with a DH, the team's pitchers (or pinch hitters) must bat for the entire game.

The designated hitter can be moved to a fielding position during the game. If the DH is moved to another position, his team forfeits the role of designated hitter, and the pitcher or another player (the latter possible only in case of a multiple substitution) would bat in the spot of the position player replaced by the former DH. If the designated hitter is moved to pitcher, any subsequent pitcher (or pinch-hitter thereof) would bat should that spot in the batting order come up again (except for a further multiple substitution). Likewise, if a pinch-hitter bats for a non-pitcher, and then remains in the game as the pitcher, the team would forfeit the use of the DH for the remainder of the game, and the player who was DH would become a position player (or exit the game).

The DH substitution rule has an exception: If a starting pitcher started simultaneously as the designated hitter, that player may remain as DH to bat for his relievers after being replaced as pitcher, likewise remaining as starting pitcher if he was pinch hit or pinch run for by a bench player who had become the new designated hitter. If that player starts the game as a designated hitter and pitches out of the bullpen, the team would lose the designated hitter once his relief appearance is over, unless he is moved to the outfield. The exception was added by MLB for the 2022 season, coincident with the introduction of the universal DH. It has been widely nicknamed the "Ohtani rule" as a nod to Shohei Ohtani, at the time a two-way star pitcher and hitter for the Los Angeles Angels who had sometimes batted for himself in the past, but had to leave games as hitter or move to another position on the field when relieved as pitcher due to the limitations of the old rule. The rule change was subsequently applied for international-level games, starting with the 2023 World Baseball Classic.

Unlike other positions, the DH is "locked" into the batting order. No multiple substitution may be made to alter the batting rotation of the DH. In other words, a double switch involving the DH and a position player (with the exception of players started as starting pitcher and designated hitter) is not legal. For example, if the DH is batting fourth and the catcher is batting eighth, the manager cannot replace both players so as to have the new catcher bat fourth and the new DH bat eighth. Once a team loses its DH under any of the scenarios already discussed, the double switch becomes fully available, and may well be used via necessity, should the former DH be replaced in the lineup.

In Major League Baseball, during interleague play between 1997 and 2021, the DH rule was applied to a game based on the rules of the home team's league. If the game was played in an American League park, the designated hitter could be used; in a National League park, the pitcher must bat or else be replaced with a pinch-hitter. On June 12, 1997, San Francisco Giants outfielder Glenallen Hill became the first National League DH in a regular-season game, when the Giants met the American League Texas Rangers at The Ballpark in Arlington in interleague play.

At first, the DH rule was not applied to the World Series. From 1973 to 1975, all World Series games were played under National League rules, with no DH and with pitchers required to bat. For 1976, it was decided the DH rule would apply to all games in the World Series, regardless of venue, but only in even-numbered years. Cincinnati Reds first baseman Dan Driessen became the first National League designated hitter in the postseason; he was the DH in all four World Series games that year. This practice lasted through 1985. Beginning in the 1986 World Series, the DH rule was used in games played in the stadium of the American League representative.