Several other players tried their hand at DH during the Astros' tenure in the NL, ranging from stars Craig Biggio, Jeff Kent, Lance Berkman and Jeff Bagwell, to little-known players such as Jack Howell, Eric Munson and Todd Self.
Prior to this season, the DH has been a novelty to the Astros, something they were forced to do a few times a year on the road in places like Boston, Baltimore and Seattle. It was never part of their routine and had no effect on how they constructed their roster.
Now, with the Astros having made an unprecedented move to the American League, the DH will be as much a part of their makeup as any other position.
"I think the DH is a luxury," Astros manager Bo Porter said. "That's what [general manager] Jeff [Luhnow] and I, when we set out to talk about the designated hitter, we wanted to have a designated hitter that could actually go in and play a position, and that's one of the reasons we targeted Carlos Pena."
Pena, 34, was signed Dec. 17 to become the Astros' first full-time DH, though he should get plenty of at-bats at first base as well. He's played 12 years in the Majors, all with AL clubs, except for one season with the Cubs. Pena has appeared in 45 games as a designated hitter, batting .243 with 10 homers and 24 RBIs in 148 at-bats.
Staying in a routine and keeping yourself involved in the flow of the game is crucial to being a successful DH, Pena said.
"There is a certainly preparation that comes into it," he said. "You come into the game the same way, knowing who's on the mound and knowing what their weaknesses are and you know what your approach is going to be on a certain pitcher that day."
Pena said that when he's the DH, he often stretches when the team is on defense and will even go into the batting tunnel beneath the stands and hit balls off a tee to keep sharp.
"There's some drills that every one of us has," Pena said. "We feel that's what makes us click. It's very important to stay active. If you just sit around, it's a very difficult thing. You have that routine, so just keep doing it."
Porter agrees, saying it's important the DH doesn't treat at-bats like four pinch-hits in one game.
"There's a craft to it," Porter said. "Some people overlook it. Everybody can't do it."
The Astros have had 24 different players get at-bats at DH since Interleague Play began in 1997, with Carlos Lee (27 games), Biggio (20), Berkman (12), Daryle Ward (11) and Bagwell (10) appearing in the most games at DH. Collectively, the Astros' DH spot has batted .270 with 17 homers and 62 RBIs in 120 games.
Bagwell didn't enjoy being the DH because it was hard for him to keep him mind in the game, though he did serve as DH in the 2005 World Series because his degenerative shoulder condition wouldn't allow him to play defense anymore.
"If you're young and really don't understand the situation, it's tough," Porter said. "You're just sitting there for two innings and now your at-bat comes around again, and it's almost like you grab the bat and it's another pinch-hit."
The DH is the most definitive difference between the leagues. It was adopted by the AL in 1973 to allow teams to designate a player to bat in place of the pitcher. The DH can only be used for the pitcher and not any other position player. Also, if the player who begins the game at DH moves to a defensive position on the field, the team forfeits the DH the rest of the game.
Luhnow said the presence of a DH could affect the roster in some subtle ways. He expects the DH role to be shared by several different players at the beginning of the year, with someone solidifying themselves into the position as the year goes on.
"At the end of the day, we're still only taking 25 players," he said. "You have to mix pitchers and hitters, and it might affect who the last bench player is, what he might be able to do because there's going to be a lot less doubles-switches and pinch-hitting and so forth."
And Porter says he'll utilize the DH to lighten the workload of players like Jose Altuve, who admittedly wore down at the end of last season. Altuve has no experience at DH, but that's where Pena's leadership comes into play.
"Altuve can go over to Carlos and say, 'OK, what's your routine when you're DHing?'" Porter said. "That will help him because that's something he's never done before."