BALTIMORE -- The Orioles lost the services of one of their best relievers Tuesday, when they placed closer George Sherrill on the disabled list with a case of inflammation in his left shoulder. Sherrill had told manager Dave Trembley that he was in pain Monday, and the team pushed him through a magnetic resonance imaging test to determine the extent of the injury.

The tests didn't show any catastrophic damage, but the Orioles placed Sherrill on the disabled list for precautionary reasons. As of now, the plan is to let Sherrill rest his tired arm for a week and then he'll resume a throwing program shortly after that. Sherrill is eligible to return from the DL on Aug. 31, and the team thinks he can return close to that date.

"It started off as a little tendinitis thing and it just exploded," Sherrill said. "It is a relief that it's not something structural. We'll just rehab it and get back as soon as possible."

"The MRI news actually was good," said Andy MacPhail, Baltimore's president of baseball operations. "The doctor told me that the MRIs, side-by-side, looked identical to the one they took in Spring Training. There is a little inflammation, which they injected [with cortisone] and prescribed rest. We don't have any long-term concerns at the time."

Trembley spoke to the media before he'd gotten the test results.

"When you look at the amount of saves we've had and the amount of games we've won, I don't think it takes a rocket scientist to figure out what a central figure he's been on our ballclub," Trembley said. "But that's looking at the glass half full, and I'm still looking at the glass up there. I'm not getting to that point until we get to that -- if in fact that's the case."

Sherrill, who has 31 saves, had been on pace to break the existing franchise record (45) in that category. The left-hander was named to his first All-Star Game in recognition of his success, but that game may have been his undoing. Sherrill worked 2 1/3 innings in the Midsummer Classic, which equaled his longest big league outing since 2004.

Since then, he hasn't been quite the same. Sherrill has made 10 appearances since the All-Star break, racking up a 1-1 record and a 5.91 ERA. Opponents have batted .295 since the intermission compared to .221 in the first half. Trembley made the connection to the All-Star Game appearance, but he wasn't quite certain it was a cause-and-effect relationship.

"That would be pure speculation," he said. "I think that would be easy to fall back on and point fingers at, and I'd prefer to take the high road and stay away from that. From my understanding, and I don't have a big background in medical physiology, these things happen over a long period of time. So the rapport that I've had with George personally, the rapport that George has had with [pitching coach Rick] Kranitz and [bullpen coach] Alan Dunn, I think has been a very clear and open line of communication. ... I did not particularly see this coming, but I'm not totally shot out of the water by it."

Baltimore will likely use Jim Johnson to close in Sherrill's absence, and veteran southpaw Jamie Walker may play a key role late in the game. The Orioles traded veteran Chad Bradford earlier in the month and will need to sort out their various relief options. Randor Bierd, Rocky Cherry and Dennis Sarfate may all have to work later in the game than usual.

As for Sherrill, who was acquired from Seattle in the offseason trade for Erik Bedard, the news could've been worse. Baltimore lost late-inning relievers Chris Ray and Danys Baez to elbow surgeries last season, so the Sherrill news was seen in a more favorable light. Surgery doesn't appear to be an option, and the Orioles hope to have him back soon.

"When you look at his workload, he'd been working about 47 innings for the last three years," said MacPhail of Sherrill. "This year, he's already exceeded that, which to some degree is just a function of his role. As a closer, you don't know when you're going to work. It could be two or three days in a row, unlike being the left-handed specialist he was in Seattle."