ATLANTA -- Roy Oswalt returned from Houston on Sunday after having his strained left hip examined, but the Astros told their ace to wait at the Atlanta airport for the team's flight to Pittsburgh.
Houston manager Cecil Cooper had no update on a prognosis for Oswalt, who is expected to throw off flat ground on Monday and have a bullpen session on Tuesday.
Oswalt improved to 7-8 after beating the Los Angeles Dodgers last Monday, but he had to leave the start because of pain in the hip.
The right-hander threw off flat ground on Friday in Atlanta, but persistent pain caused the Astros to send him to see Dr. Mike McCann the following day in Houston.
Despite beginning the year with more victories (112) than any pitcher since the start of 2001, Oswalt has struggled to a 4.60 ERA, 53 points higher than the average he posted over his first six seasons.
Cooper said for the second straight day that he doesn't know when Oswalt could start again.