Substitutions and designated hitter
Baseball substitutions and designated hitter: lineup changes explained
How batting-order substitutions, pinch hitters and runners, defensive replacements, pitching changes and the designated hitter work — and where competition rules differ.
Replacing a player keeps the lineup slot
In standard MLB and WBSC rules, a substitute takes the batting-order position of the player being replaced. Once a player is removed for a substitute, that player cannot return to the game. Changes are normally made while the ball is dead and are recorded by the umpire.
Pinch hitters, pinch runners and defensive replacements
A pinch hitter bats for another player, a pinch runner replaces a runner on base, and a defensive replacement enters to field. The substitute then remains tied to the replaced player’s lineup position, so a late-game move can affect both offense and defense.
What the designated hitter actually does
The designated hitter (DH) bats in place of the pitcher in rulesets that use the DH. The pitcher still plays defense, so the DH is not simply a tenth fielder. Current MLB uses the DH in both leagues, and the WBSC 2025-2026 rules also include a designated hitter rule; other competitions may modify or omit it.
Pitching-change rules are not universal
Do not assume every competition uses the same pitching-change restriction. MLB uses a three-batter minimum or the end of a half-inning, with injury or illness exceptions. The WBSC 2025-2026 base substitution rule instead requires a new pitcher to complete the current batter or retire the side, unless injury or illness prevents it. Tournament regulations can add further rules.