"It's going to give Casey Coleman an opportunity to pitch," manager Mike Quade said. "He obviously doesn't have the experience or quality that Z had, but maybe he'll show up and be the guy that we saw last year for a while."
Coleman has made 11 appearances for the Cubs this year -- nine of them starts -- and compiled a 2-4 record with a 7.23 ERA before being optioned to Iowa. He's 5-2 with a 3.65 ERA in 12 Triple-A starts.
The Cubs weren't sure on Saturday night whom they would call up. Coleman's start wouldn't be needed until the middle of next week, so they could have been afforded the luxury of calling up a reliever or position player.
"We used some pitching yesterday. We were trying to decide on pitching or a regular for a couple days," Quade said. "I could just see me putting a regular on a plane last night and us using a lot of bullpen today and get to Houston going, 'How stupid was that?'"
Coleman was scheduled to start for Iowa on Wednesday against Salt Lake, so he'll be pitching against the Astros on regular rest.