Runs were hard to come by when the Colorado Rockies and the Houston Astros played two games in Texas this week.

Coors Field in Denver could be a different story when the teams play the second half of their four-game set Wednesday and Thursday.

The host Astros won 2-1 in 11 innings on Tuesday to sweep the two games in Houston. Monday's game also was a 2-1 win.

Colorado rookie right-hander Ryan Castellani will go against Astros lefty Framber Valdez on Wednesday night.

Castellani is making his third start since moving into the rotation to replace Chi Chi Gonzalez, who is out with a biceps injury.

Castellani threw four scoreless innings in his debut at Seattle on Aug. 8, and allowed just one run in 4 2/3 innings against the Texas Rangers on Friday. Castellani (0-0, 1.04 ERA) has struck out 10 and walked three in his two starts.

"He showed a lot of confidence," Rockies shortstop Trevor Story said last weekend. "He's a competitor, and he's out there showing it. He's definitely not scared. The moment's definitely not too big for him. He's just going out there and letting it eat."

Valdez (1-2, 1.90 ERA) has pitched better than his record this season. Wednesday will be his fourth start and fifth appearance overall. He lost his season debut to the Los Angeles Dodgers on July 28, giving up three runs in 4 1/3 innings and has been better in August.

He was a hard-luck loser at Oakland on Aug. 8, allowing two runs -- one earned -- in seven innings in a 3-1 loss to the A's. That came after a relief appearance of 6 1/3 shutout innings at the Los Angeles Angels.

He got his lone win in his last start, Friday against Seattle, when he allowed one run in six innings.

He has done well enough to impress Houston's first-year manager Dusty Baker.

"A young man with that much talent, you don't really know what expectations he's supposed to exceed," Baker said recently. "I heard he had some bouts of wildness in the past. But now, when he starts losing it, he backs off the mound.

"I had talked to him earlier in the spring (and told him) that we were counting on him because everyone in the league knows what kind of stuff he has. It's just a matter of him throwing strikes," Baker said.

Like Castellani, Valdez will be facing an opponent for the first time Wednesday night.

The Rockies have had some roster issues arise over the past couple of days. Monday night, catcher Elias Diaz was put on the restricted list for a violation of COVID-19 protocol, according to MLB.com, and righthander Ashton Goudeau was recalled from the alternate training site.

On Tuesday, outfielder David Dahl was scratched from the lineup with back tightness. There could be more changes on the way if the organization's top prospect, infielder Brendan Rodgers, who was with the team in Houston as part of the taxi squad, is activated.

Rodgers made his major league debut last season but struggled with a right shoulder injury. His season ended when he had surgery on a torn labrum. He was not part of the Opening Day roster last month but he could join the team soon.

"We're past the shoulder woes," manager Bud Black said. "He feels 100 percent as far as his ability to play short, to play second and make all the throws without any discomfort in the arm, and offensively swinging the bat."