Berkman has been on the disabled list since July 23 with a left calf strain and didn't travel with the team to Chicago earlier this week because of a death in the family. Oswalt left Tuesday's start at Wrigley Field with a left lower back strain and went to Houston the following day to get an injection.
Oswalt played light catch in the outfield prior to Friday's game and said he still felt sore. He was originally scheduled to start Sunday's series finale, but Bud Norris will take his spot and make his first Major League start.
"It feels better than when it happened," Oswalt said. "If I had to pitch today, I couldn't. I can get around pretty well. I could do 90 percent of the jobs in America. It's the other 10 percent, one of them being mine, that I can't do."
The Astros will wait until Monday before deciding whether to put Oswalt on the disabled list. Houston is in need of a starter Tuesday after Russ Ortiz was placed on unconditional release waivers following his woeful outing Thursday in Chicago. Oswalt will slide into Ortiz's spot if he improves.
"If I go on the DL, I would only miss two starts with the off-day [Thursday]," he said.
Oswalt's injury stems from the herniated disk he was diagnosed with last year. The disk is pressing on a nerve that runs down his leg and has been causing his left leg to go numb. Manager Cecil Cooper admitted the disabled list is a possibility.
"But we have to wait until Monday," he said. "He's had the shot, so let's give it some days to work."
Meanwhile, Berkman hit off a tee in the batting cage and is pain free, but he won't be able to gauge his calf until he begins running, which he hopes to do Monday.
"When I first went on the DL, I wasn't sure I needed to go on it, and now I'm glad I did because it's really something that has lingered, even though I haven't been playing," Berkman said. "I am anxious to get back out there, but only when I feel like I'm 100 percent, or at least good enough to where I'm not going to have any setbacks."
Norris, who gave up one run and three hits in his Major League debut Wednesday in Chicago, is eager to make his first start Sunday. He led the Pacific Coast League in ERA and strikeouts before being called up after 19 starts.
"I'm excited about that," he said. "I've been throwing out of the 'pen, but I definitely want to starter and see how that goes. I'm looking forward to it, and it should be a good time."
Brian McTaggart is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.