Oswalt is on the disabled list with lower back inflammation. He lacked his typical fastball velocity Thursday in a rehab start with Class A Clearwater, but Phillies general manager Ruben Amaro Jr. said he is not concerned.
"Typically I think there would be [concern], but for a guy like that I think adrenaline means a lot," he said. "No disrespect to the Florida State League, but I just don't know if there's the same juice that you have. But at the same time we'll have to monitor him. If he doesn't have the same velocity and you continue to show that on the mound with us, then I'll have to keep my eye on it. But he doesn't have anything physically wrong with him. He feels fine."
The Phillies will need to make a roster move when Oswalt is activated. The two most likely candidates to be optioned are right-handers Scott Mathieson and Vance Worley.
"He's pitched well in a couple of different roles, but his best role for us is as a starter in case somebody goes down, because we don't have a lot of depth there," Amaro said of Worley. "At some point we'll have to make a decision when Oswalt comes on about what we're going to do with Worley and other guys."
Amaro said recently the organization is better served with Worley continuing to start in Triple-A Lehigh Valley. Asked if his thinking could change based on Worley's recent effectiveness in the bullpen, Amaro said, "That could change. We haven't made any decisions yet. But as I said, we don't have a whole lot of depth in our rotation. You've got a situation where Oswalt hasn't pitched in a while. We've got [Joe Blanton's] situation with his elbow, where there's some question about it, even though we think he's moving forward. We need starting-pitching depth. [Kyle] Kendrick did a nice job of spot starting, but we need to have as many guys stretched out as we can. That's the strength of our club. I don't want to weaken it."