Left-hander Wandy Rodriguez for the Astros and right-hander Juan Nicasio for the Rockies will oppose each other in the first game.
The Rockies will come back with right-hander Alex White, making his fourth start of the season, in the nightcap while the Astros will call up right-hander Jordan Lyles.
Rodriguez is 4-4 this season with a 2.14 ERA, which before Sunday's games was fourth-best in the National League and third among left-handers.
In his last outing, Wednesday against the Cubs, Rodriguez allowed a run in the first inning, and then held them scoreless over the next six frames. He struck out five, and his seven innings marked the fourth time he's lasted that long in his past five starts.
Rodriguez handled the Cubs with less than his best stuff.
"I didn't feel very good with my fastball today," Rodriguez said after the game. "I used a lot of my breaking balls because I didn't have a good [fastball] tonight."
The Astros lefty is the type of pitcher who can win even if his best pitch isn't working, manager Brad Mills said.
"It's a testament to [Rodriguez] as a pitcher that he's able to utilize other stuff," Mills said. "We always know he's got that good breaking ball, but he's able to utilize that changeup, and then if the fastball is not coming out of his hand real well, he's going to try to spot it the best he can."
Rodriguez last started against the Rockies on Opening Day and got a no-decision because of three unearned runs in 6 1/3 innings.
Nicasio is 2-2 with a 4.83 ERA and has lost his past two decisions.
In his last outing Tuesday at Miami, Nicasio allowed six runs (five earned) and nine hits in five innings in a 7-6 loss to the Marlins.
The Rockies staked Nicasio to a three-run lead in that game, but he could not hold it.
"I don't know what happened with me," Nicasio said, who denied he was suffering any lingering effects from being hit in the hip by a line drive in his previous game.
Nicasio was 4-4 with a 4.14 ERA in 13 starts for the Rockies last season.
Astros: Lyles recalled for nightcap
Lyles, 21, will be recalled from Triple-A Oklahoma City to make his fourth start of the season. He's 0-1 with a 5.29 ERA. A new rule this season allows for a 26-man roster on doubleheaders scheduled more than one day in advance, which means Lyles' callup will be temporary.
"I'd like to have the 26-man rule all the time," Mills kidded. "But yeah, it's real good, definitely for a doubleheader like this."
Left-handed reliever Xavier Cedeno's contract was purchased Sunday from Oklahoma City after lefty Fernando Abad was placed on the 15-day disabled list with a strain on his right side.
Cedeno faced one batter Sunday, walking Bobby Abreu with the bases loaded in the seventh inning.
Rockies: White hoping to bounce back
White, the second-game starter Monday, last pitched Wednesday, going six innings and allowing four runs and eight hits in an 8-4 loss to the Marlins.