In addition, unlike other positions, the DH is "locked into" the batting order and 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 is not possible. 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 discussed in the previous paragraph, however, the double switch becomes fully available, and may well be used via necessity, should the former DH be replaced in the lineup.
In games where a team from a league using the DH rule plays against a team from a league not using the DH rule (e.g., interleague play, the World Series), the rules of the home team's league apply to both teams.
There have been times when a manager may willingly surrender the DH position late in a game. During the 2005 American League Division Series between the New York Yankees and the Los Angeles Angels of Anaheim, New York had Bernie Williams slated as the designated hitter. Late in the game, manager Joe Torre took Williams out of the DH and put him in center field because of Williams' superior defensive play. Since the Yankees already had the lead, not giving up any more runs was more important to Torre than having a better hitter hit for the pitcher in the game at the time, Yankees closer Mariano Rivera. Because a double switch was used, it was not necessarily a negative situation to have Rivera bat. Rivera's place in the order would only come up if the Yankees had batted around, which would have automatically increased their lead very late in the game, giving more cushion for the Yankees' best relief pitcher to close out the game.
On May 19, 2008, the Minnesota Twins surrendered their DH position in a game vs. the Texas Rangers in Minneapolis. Twins Manager Ron Gardenhire had to use rookie pitcher Bobby Korecky as a hitter in the 11th inning of the game, who had only pitched in five games prior and had never had a major league at-bat. However, Korecky hit the first pitch he saw into right field for a single, becoming the first Twins pitcher to get a hit in an American League game since the implementation of the DH rule. The inning ended with Korecky stranded at 3rd base with the bases loaded. Korecky ended up getting his first major league win in this game as the Twins won 7-6 in 12 innings.
On June 11, 1988, New York Yankees manager Billy Martin made the unusual choice to insert a starting pitcher into the DH slot, Rick Rhoden, who was known as a superior hitting pitcher. Rhoden went 0 for 2 with a groundout and a sacrifice fly to right field, earning him an RBI. He was pinch hit for by José Cruz in the Yankees' 8-6 victory over the Baltimore Orioles.
There were three occasions where a team elected not to start a designated hitter in an American League ballgame. The pitchers for those games were Ferguson Jenkins on October 2, 1974 for the Texas Rangers at Minnesota,, Ken Brett for the Chicago White Sox on July 6, 1976 against the Boston Red Sox,, and Brett again on September 23, 1976 for Chicago against the Twins.
The rationale for the designated hitter rule is that, with a few exceptions — most notably Babe Ruth, who began his career as a pitcher with the Boston Red Sox — pitchers are usually weak hitters who ordinarily perform once every four or five games. The designated hitter idea was first floated by Philadelphia Athletics manager Connie Mack in 1906. In the late 1920s, National League president John Heydler made a number of attempts to introduce a 10th man designated hitter as a way to speed up the game, and almost convinced National League clubs to agree to try it during spring training in 1929. However, momentum to implement the DH did not pick up until the pitching dominance of the late 1960’s. In 1968, Denny McLain won 31 games and Bob Gibson had a 1.12 ERA, while Carl Yastrzemski led the American League in hitting with a .301 average. After the season, the rules were changed to lower the mound from 15 to 10 inches and change the upper limit of the strike zone from the top of a batter's shoulders to his armpits. In addition, in 1969 spring training, both the American League and National League agreed to try the designated pinch hitter (DPH), but they did not agree on the implementation. Most NL teams chose not to participate. On March 6, 1969, two games utilized the new DPH rule for the very first time. Two newly formed expansion teams, the Montreal Expos and the Kansas City Royals would participate in one such game, and the New York Yankees and Washington Senators in the other. On March 26, 1969, Major League Baseball nixed the idea for the time being. Like other experimental baseball rule changes of the 1960s and 70's, the DH was embraced by Oakland A's owner Charlie O. Finley. On January 11, 1973, Finley and the other American League owners voted 8-4 to approve the designated hitter for a three-year trial run.
On April 6, 1973, Ron Blomberg of the New York Yankees became the first designated hitter in Major League Baseball history, facing Boston Red Sox right-handed pitcher Luis Tiant in his first plate appearance. "Boomer" Blomberg was walked.
Naturally, the result of the first season of the DH was that the American League posted a higher batting average than the National League, something which has remained consistent to this day.
The designated hitter offers American League managers two options in setting their teams' lineups: they can either rotate the role among players (for example, using a left-handed hitting DH against a right-handed pitcher and vice-versa) or they can employ a full-time designated hitter. It also allows them to give a player a partial day off. The adoption of the designated hitter rule has virtually eliminated the use of the double switch in the American League.
At first, the DH rule was not applied to the World Series. In 1976, it was decided the rule would apply to all games, regardless of venue, but only in even-numbered years. This practice lasted until 1985. The next year, the rule was adapted to its current format of only applying in games played in the American League team's stadium.
Similarly, there was initially no DH in the All-Star Game. Beginning in 1989, the rule was applied only to games played in American League stadiums. When this occurs, fans are allowed to select an AL player to start at that position, while the NL's manager decides that league's starting DH. When regular season interleague play was introduced in , the rule was, and continues to be, applied in the same fashion. On June 12, 1997, San Francisco Giants outfielder Glenallen Hill became the first National League player to be the DH in a regular-season game against the American League's Texas Rangers at The Ballpark in Arlington, when they met in interleague play. When the Milwaukee Brewers moved from the AL to the NL in 1998, the Brewers no longer used the DH on a regular basis; thus, as also usually happens when a minor-league pitcher joins an NL team, their pitchers needed to take batting practice.
Occasionally National League teams utilize the designated hitter during spring training games, usually when a player is recovering from an injury.
In recent years, full-time DHs have become less common, and the position has been used to give players a partial off-day, allowing them to bat but rest while the other team is batting. Only a handful of players compile over 400 at-bats as a DH each year.
Opponents of the DH rule argue that use of the designated hitter introduces an asymmetry to the game by separating players into classes, creating offensive and defensive specialization more akin to American Football. When the pitcher bats, all nine players take turns at the plate and in the field. This is not so with the DH rule, and opponents of the rule believe it effectively separates pitchers, other fielders, and designated hitters.
While the DH is batting in what would be the lineup spot for the pitcher, the pitcher may be inserted into another spot in the lineup when the DH role is terminated, inconsistent with the principle that a player's position in the lineup is fixed for the entire game.
The designated hitter rule also changes manager strategy in late innings. Traditionally, a manager must decide when to let a pitcher bat or remove him, as well as who to pinch-hit with and where or if that player should take the field afterward. When the decision to remove a pitcher is made, the manager may also elect to double switch, delaying the new pitcher's turn at bat.
On the opposite side, a manager in a close game may have to choose whether or not to pitch around a DH in the late innings, possibly granting an intentional base on balls to avoid a potentially hard-hitting slugger in place of a relatively weak pitcher, while an NL manager will not have to choose whether or not to give up a base runner (and the associated wear and tear on his pitcher's arm) to avoid a DH.
Advocates of the DH point to the fact that it has extended many careers, and, in a few cases, created long, productive careers for players who are weak fielders or have a history of injuries, such as Edgar Martínez. Moreover, Hall of Fame members George Brett, Carl Yastrzemski, and Paul Molitor were able to extend their prolific careers by a few years as designated hitters. Dick Stuart, a notoriously poor fielder, played before there was a DH rule. Critics of the DH reply that creating or extending the careers of poor fielders is not necessarily a good thing, because they say it merely promotes 'batting cage' players whose only real skill is their ability to swing the bat.
Games played with the DH allow pitchers to play deeper into games than they otherwise might, by removing the manager's incentive to remove a pitcher from play in order to attain a short-term offensive advantage. Also, since a pitcher's typical offensive "contribution" is at best to advance the runner by sacrificing himself and at worst as a rally-killing double play, it improves the play of the game to remove an "easy out" player from the batting order. This is also the only baseball strategy removed by the addition of the designated hitter is the double switch; if anything, modern American League baseball with its array of specialist pitchers and batting styles is much more complex than baseball before 1973. However, the designated hitter encourages beanball wars by removing the pitcher from the batting order, where he might be subject to retaliation.
There is a significant difference in the preparation required between hitting and pitching. A pitcher is quickly worn down by his position and can only start every 4-5 days or pitch 1-2 innings of relief for 2-3 consecutive days. Sports like basketball, football, hockey, and soccer offer no equivalent where one position is much more physically taxing than all others. A hitter hits better when he is able to play regularly and fine tune his swing, judgment of the strike zone, and comfort with different pitchers and pitches. This is especially important early in hitters' careers and hitters who could be valuable to their major league club as reserves are often kept in the minors so they can play every day and develop their skills. Pitchers need rest, hitters need reps. Occasionally a pitcher can be effective on short rest in the playoffs or an NL pitcher or pinch hitter who only appears once every five games can post good statistics with limited at bats, but those are not common. Even most full time pinch hitters or utility players are former major or minor league regulars who had years to develop their hitting skills. The DH rule does not just extend the careers of aging sluggers, it also saves pitchers from the overwhelming difficulty of being asked to perform the task of batting with 8 batters who bat about 5 times as often.
There is considerable debate over whether the designated hitter rule should be continued. Some have even argued that the National League should adopt it full time. There are also fans who enjoy the fact that the different leagues use different rules, arguing that there should be some differences between the American and National Leagues and the Designated hitter is a fine example of that. Two generations of fans of American League teams have grown up with the Designated Hitter rule being in place, and for them, the DH is as much a traditional part of baseball as the pitcher batting is for fans of National League teams.
With the rule, the quality of play may suffer because the home team automatically receives a significant unnatural advantage no matter what league's rules are in effect. To combat this, Major League Baseball Commissioner Bud Selig has proposed that the road team's rules would be followed for interleague games. It has proven to be an unpopular proposal.
An example of criticism is in an Interleague game between the Houston Astros and New York Yankees in Houston on June 15, 2008. With the NL's no-DH rule Yankees ace pitcher Ching-Ming Wang was forced to hit. Wang reached base on a fielder's choice. Two batters later Wang was on second base with Yankees' second base Robinson Cano on third, Yankees' center fielder Johnny Damon on first base and Yankees' shortstop Derek Jeter batting. Jeter hit a single and Cano and Wang scored. However, Wang was injured and started limping half way towards home. Wang left the game with an injured foot. After the game the Yankees learned that Wang would be out until September with sprained and torn foot ligaments. Two days later, hours before the Yankees home Interleague game against the Padres at Yankee Staduim, their co-chairman Hank Steinbrenner complained about the NL not having the DH rule.
One notable exception to the NFHS designated hitter rule in youth baseball is American Legion baseball. Legion rules exactly follow those prescribed in the Official Baseball Rules, which allow the DH only to bat for the pitcher. Prior to 1995, the use of the DH was not allowed in Legion baseball.
In college baseball, NCAA rules state that the designated hitter must hit for the pitcher, but in many instances the pitcher is also a good hitter, and the coach may elect to let the pitcher bat in the lineup. If the pitcher opts to bat for himself, he is treated as two separate positions — a pitcher and a designated hitter (abbreviated P/DH on the lineup card) — and may be substituted for as such (i.e. if he is removed as the pitcher, he may remain as the designated hitter and vice versa). However, if a player who starts a game as a P/DH is relieved as the starting pitcher, he may not return to the mound even if he remains in the game as the DH, and he may not play any other defensive position after being relieved as the pitcher. Conversely, a player who begins the game as the DH, but not as the pitcher, may come into the game as a reliever and remain as the DH (in effect becoming a P/DH), be relieved on the mound later in the game but continue to bat as the DH.
"The average fan comes to the park to see action, home runs. He doesn't come to see a one-, two-, three- or four-hit game. I can't think of anything more boring than to see a pitcher come up, when the average pitcher can't hit my grandmother. Let's have a permanent pinch-hitter for the pitcher." - A's Owner Charlie O. Finley
"I'm not an advocate of the Designated Hitter Rule; I'm only an advocate of seeing the truth and telling the truth. What the truth comes down to here is a question of in what does strategy reside? Does strategy exist in the act of bunting? If so the Designated Hitter Rule has reduced strategy. But if strategy exists in the decision about when a bunt should be used, then the DH rule has increased the differences of opinion which exist about that question, and thus increased strategy...[the research shows] that there is more of a difference of opinion, not less, in the American League." - Bill James in The Bill James Historical Baseball Abstract (1986)
"Everyone in the world disagrees with me, including some managers, but I think managing in the American League is much more difficult for that very reason (having the designated hitter). In the National League, my situation is dictated for me. If I'm behind in the game, I've got to pinch hit. I've got to take my pitcher out. In the American League, you have to zero in. You have to know exactly when to take them out of there. In the National League, that's done for you." - Jim Leyland
"I've got my pitchers running the bases, and one of them gets hurt. He's going to be out. I don't like that, and it's about time they address it. That was a rule from the 1800s." - Hank Steinbrenner