The designated hitter changes the lineup, not the defense.

How to read a DH situation

1. Confirm that the competition is using the designated hitter rule for that game.
2. Check the official lineup card to see whether a DH was listed before the game started.
3. Identify the DH's batting-order spot and the pitcher for whom the DH is batting.
4. Track any pinch-hitter, pinch-runner, defensive move, or pitching move involving the DH, pitcher, or a player who becomes pitcher.
5. If the DH is lost, place the pitcher into the batting order under the substitution rule and continue without a DH.

The DH bats for the pitcher

The designated hitter is a player listed in the batting order to hit instead of the pitcher. The pitcher remains one of the nine defensive players. The DH has a batting-order spot but no defensive position unless the manager later moves that player onto the field.

The rule is common in professional baseball, including MLB. Other levels can differ. Some amateur, youth, school, and tournament rulebooks use no DH, an optional DH, or expanded versions such as an extra hitter. Always check the rule set for the competition being played.

The DH must be selected before the game

A team cannot wait to see how the game develops and then create a DH later. If the designated hitter is used, that player is named on the starting lineup card before the game. If a team chooses not to list a DH when the game starts, it plays without a DH for the rest of that game.

In MLB, the starting DH must bat at least once unless the opposing team changes pitchers before that plate appearance. That prevents a team from naming a DH only as a temporary placeholder and replacing that player immediately under ordinary conditions.

A substitute for the DH becomes the DH

If a pinch-hitter bats for the DH, that pinch-hitter becomes the new DH. If a pinch-runner runs for the DH, that pinch-runner becomes the new DH. The batting-order spot stays the same; only the player occupying that DH spot changes.

The normal substitution principle still applies: once a player has been removed from the game, that player cannot return unless the competition has a special re-entry rule. MLB does not use free re-entry, but some youth and school rules do.

Some moves end the DH for that team

The DH is not guaranteed for the whole game. In MLB-style rules, a team loses the DH if the DH takes a defensive position. The former DH keeps batting in the same lineup spot, but the pitcher must then enter the batting order in the spot of the defensive player who left the game, unless multiple substitutions allow the manager to assign the new spots legally.

A team also loses the DH if the pitcher moves from the mound to another defensive position, if the current pitcher pinch-hits or pinch-runs for the DH, or if another player pinch-hits for a player other than the pitcher and then becomes the pitcher. After the DH is lost, that team cannot restore it later in the same game.

A starting pitcher can also be the DH

Modern MLB rules allow a starting pitcher who bats for himself to be treated as two roles for DH purposes: pitcher and designated hitter. If that player is removed as pitcher, he can continue as the DH. If he is removed as DH, he can continue pitching but no longer bats for himself.

This is a special rule for the starting pitcher listed as both pitcher and DH. It should not be treated as a general rule that any pitcher can freely move in and out of the batting order.

The DH is not a tenth fielder

The DH does not create an extra defensive player. The defensive team still has nine fielders: pitcher, catcher, four infielders, and three outfielders unless it uses an unusual legal alignment. The DH simply replaces the pitcher's turn at bat in the batting order.

Because the DH is tied to the pitcher for batting purposes, most lineup complications happen when the manager tries to move the DH onto defense, move the pitcher to another position, or make a substitution that blurs who is batting for whom.

Misunderstandings to avoid

• "The DH can be added later" is wrong under MLB-style rules. If no DH is listed before the game, the team cannot create one during the game.
• "The DH can play defense and stay as DH" is wrong. Once the DH enters defensively, the team loses the DH.
• "A pinch-hitter for the DH is just a normal pinch-hitter" is incomplete. That player becomes the new DH in the same lineup spot.
• "The pitcher never bats in a DH game" is incomplete. The pitcher can enter the batting order if the team loses the DH, and a starting pitcher may be listed as both pitcher and DH under current MLB rules.
• "Every baseball league uses the same DH rule" is wrong. The availability and details of the DH vary outside professional rule sets.

How the lineup changes

• DH is pinch-run for in the sixth inning: the pinch-runner becomes the DH and bats in that same spot later.
• DH moves to first base: the team loses the DH. The pitcher must be placed into the batting order according to the substitution rules.
• Pitcher moves to left field while a reliever enters: the team loses the DH because the pitcher moved to another defensive position.
• Starting pitcher is listed as pitcher and DH, then leaves the mound: in MLB, he may remain in the game as DH if the substitution is made under the two-way starter rule.

Next baseball topics

• Mound visits and pitching changes
• Pitch clock rules
• Strike zone and check swing rules
• Back to baseball overview

Source material

• MLB Designated Hitter Rule Glossary
• MLB Designated Hitter Position Glossary
• MLB Official Information
• Little League Rules, Regulations, and Policies