Back injury lands Roy Oswalt on DL

PHILADELPHIA -- The Philadelphia Phillies remained unsure Friday exactly what was wrong with Roy Oswalt or how long he's been battling back issues. But as they were awaiting the results of an MRI on Friday afternoon, they placed him on the 15-day disabled list and hinted that he could have a prolonged absence.

Phillies general manager Ruben Amaro Jr. said the team was prepared to "take the proper amount of time to get him back and healthy and 100 percent." But Amaro said he wasn't ready to speculate on how long that might be.

He revealed that Oswalt has had "a couple" cortisone shots in his back over the last two months but wasn't certain whether he would have another in the wake of his early exit, after two innings, from his start Thursday in St. Louis.

"We're not sure what the course of action is going to be until ... we get more information from our medical people," Amaro said.

Oswalt has battled lower-back issues for several years but hadn't had a recurrence of those problems as a Phillie until his third start of this season, on April 15, when he left a start against the Florida Marlins after straining a back muscle while running to first base.

He won his next start but since then has won only once in eight starts (1-6, 4.75 ERA), wrapped around a stay on the disabled list. His velocity has been down. He had had trouble finishing his changeup. And he has allowed an uncharacteristic 77 baserunners in only 47 1/3 innings, while allowing opponents to hit .318 against him.

But neither Amaro nor manager Charlie Manuel would reveal exactly how long Oswalt has been pitching hurt.

"I don't know," Manuel said, "because he always wants to pitch. He always says he can go. ... I don't know when he was completely healthy.

"I think we've got to make sure that he's healthy, because he doesn't talk a whole lot," Manuel said. "He doesn't say too much. He always says, 'I can go,' and things like that. But at the same time, you know what? I think it's time for him to get well."

The most immediate effect of Oswalt's trip to the DL is that he will miss a start against the Boston Red Sox next Wednesday. Cliff Lee, Oswalt and Cole Hamels had been scheduled to start against Boston in that series. But Manuel said Kyle Kendrick would take Oswalt's place in the rotation. The Phillies called up right-hander Scott Mathieson from Triple-A Lehigh Valley to replace Kendrick in the bullpen.

In another roster move, the Phillies released left-handed reliever J.C. Romero, who had been designated for assignment on June 16. Amaro said the Phillies asked Romero to go to Lehigh Valley, but he declined and became a free agent.

Jayson Stark is a senior writer for ESPN.com.