A designated hitter (DH) or “tenth player,” is a member of a baseball team who bats for the pitcher, who typically has a relatively low batting average, compared to other players. In 1973, Major League Baseball (MLB) changed the rules to allow for another player to hit in the pitcher's place in order to increase hits and scores. The designated hitter plays in the American League, but the National League still has the pitchers take their designated turn at bat. If a National League team plays in an American League park, the DH will be used by both teams. If the game is at a National League park, the pitchers for both teams will take their assigned turns at bat.
In general, this player can only hit the ball; he cannot play a defensive position. If the player is assigned a defensive position in the middle of a game, than he can no longer bat for the pitcher. Instead, the pitcher will have to bat when his turn comes to bat.
If this player does take a field position during a game, however, another designated hitter can be assigned for the pitcher’s spot. The rule here is that the hitter cannot currently be playing the game. In other words, he cannot come from the current lineup. Teams often will have several players on reserve who can sub in throughout a game, however.
A coach or manager of a team may employ this strategy to attack weaknesses in the other team’s pitcher. For example, a hitter who is left-handed might be subbed in to defeat a right-handed pitcher, or vice versa.
There have only been a few players who worked full time as a designated hitter. Normally, players want to play all aspects of the game, but having the option to play in this role means that the team can bring in new players to refresh the game or to give someone a rest who is clearly not performing well. Minor league teams now also often use this position as well, filling it as needed by players who are not currently in the lineup.
Some baseball purists feel that employing a designated hitter is a corruption of the original intent of baseball. They feel a baseball team, with both its good and bad players, should play through the game. Using a player to hit in place of the pitcher, they argue, takes away from the flow of the game and the natural strengths and weaknesses of the nine men playing.
Other baseball fans applaud the use of this player, since it tends to mean that there will be more action in a game. They argue it is not particularly fun to spend time and/or money watching a bad hitter strike out, when they could be watching a good man at bat have a hit or score a run.