DENVER -- In addition to calling up Game 2 starter Jordan Lyles to be their 26th man for Monday's doubleheader against the Rockies, the Astros also optioned right-handed reliever Enerio Del Rosario to Triple-A Oklahoma City and recalled right-hander David Carpenter.

Del Rosario gave up three hits and two runs in 1 2/3 innings in Sunday's loss to the Dodgers and had a 9.00 ERA in four appearances. Carpenter opened the season with the Astros before being sent down May 15 after going 0-2 with a 4.02 ERA in 14 games. He appeared in four games at Oklahoma City.

"They felt he was throwing the ball well enough to be called up, and with Enerio throwing [Sunday] this gives us a full bullpen for today, as well," Astros manager Brad Mills said.

Under a new rule, the Astros were able to add a 26th player to their roster for the doubleheader against the Rockies and added Lyles. The young right-hander showed up at the ballpark hours before Monday's first game before his teammates urged him to go back to the hotel and get more rest in advance of his start.

Mills could use Myers in both games of twin bill

DENVER -- Astros manager Brad Mills said he won't be shy about using as many players as he feels necessary in both games of Monday's doubleheader, and that includes relief pitchers. In fact, Mills spoke with closer Brett Myers on Sunday and asked him if he would be available to pitch in both games of the doubleheader.

"He said, 'I'll be available any time you need me. If it's a save situation, I want to be out there,'" Mills said. "The reason I went to him is because that's going to determine a lot how you use your bullpen, especially in the first game. Knowing that going forward is going to help how we utilize guys for sure."

Because doubleheaders, especially scheduled doubleheaders, are a rarity these days, most of the Astros' players had yet to play in one in the Major Leagues. It can be a unique challenge, but shortstop Jed Lowrie -- who has played in quite a few weather-caused doubleheaders during his days in Boston -- says players have to have the same approach.

"You just have to play like a normal game," Lowrie said. "You knew we were going to have two games today, but we have the off day [Tuesday] and you can get in a routine. You can't really pace yourself in that situation, because you know you're going to have [Tuesday] off, so you play it like you normally would."