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08/05/09 3:17 PM ET

Oswalt, Rodriguez feeling much better

Injured pitchers could return soon; Berkman still ailing

HOUSTON -- While Roy Oswalt and Wandy Rodriguez, the lynchpins of the Astros' starting rotation, are closer to returning to the rotation, first baseman Lance Berkman will likely be out through the weekend series against Milwaukee.

Oswalt, who left his July 28 start at Chicago after 1 2/3 innings with a strained left lower back, is eyeing a possible return to the rotation Monday or Tuesday after throwing 40 to 50 pitches on flat ground in the Minute Maid Park outfield Wednesday. He will throw in the bullpen Friday, but said he noticed marked improvement from his Monday bullpen session.

"Compared to the other day, I feel a lot better," he said. "Yesterday was good and today was good. I'm going to try to throw a bullpen Friday and see how it feels."

Rodriguez, who suffered a strained right hamstring Saturday in St. Louis, could return to the rotation Sunday. He threw 25 pitches consisting of fastballs and changeups at 75 percent in the bullpen Wednesday and reported no problems.

"I felt great," he said. "I have another bullpen Friday and I'm going to throw 100 percent, and if I feel great, I can pitch Sunday."

Astros manager Cecil Cooper said Mike Hampton will start Saturday against Milwaukee and will perhaps be followed by Rodriguez on Sunday. Brian Moehler is tentatively scheduled to pitch Monday, but he could be pushed back a day if Oswalt progresses.

"It's tough in a lot of regards, but you still have to suck it up and go," Cooper said. "It's a 25-man roster, and I say all the time that everybody should be able to contribute and you need contributions from all over to be successful."

Berkman likely won't be ready to be activated from the disabled list until next week at the earliest. He's eligible to come off Friday, but his strained left calf is healing slowly.

"I've watched him run, I've seen him hit and I don't see him being ready by Friday," Cooper said.

The Astros were also without center fielder Michael Bourn on Wednesday. Bourn left Tuesday's game against San Francisco with a minor groin strain.

Brian McTaggart is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.