The Astros revealed a few minutes later Oswalt would be given an extra two days of rest before he makes his next start because of what he said was a sore right wrist. Oswalt (2-3, 4.66 ERA) will make a start Saturday in Arizona against the Diamondbacks.
"It's not a big deal," Oswalt said. "I just need a few extra days."
Oswalt, who was originally scheduled to pitch in Thursday's series finale against the Chicago Cubs, was rocked for nine hits and six runs in six innings against Pittsburgh on Saturday. Oswalt characterized the injury as "more tendinitis than anything."
As a result, the Astros shuffled their rotation. Russ Ortiz, who pitched 4 1/3 innings of scoreless relief against the Pirates on Sunday, will start Thursday. Left-hander Mike Hampton will take the mound for Friday's series opener at Arizona.
"I thought an extra [two] days would help," Oswalt said. "I think they wanted two righties to throw against Chicago."
Oswalt said the wrist bothers him when he throws breaking pitches, but reiterated to reporters the injury wasn't a concern. General manager Ed Wade shared those sentiments.
"I'm not worried to the extent the doctors and trainers have called me and said this is something we have to be worried about," Wade said. "Obviously, if he's got an issue we need it to be resolved, so we pushed him back in the rotation. The last thing we need is for our No. 1 starter to be out for an appreciable amount of time."
Felipe Paulino, who left Sunday's game after 1 2/3 innings because of a strained groin, remains day-to-day, Cooper said.
Brian McTaggart is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.