BALTIMORE -- A Mariners pitching staff that can't afford to lose many more players was dealt another blow on Wednesday when reliever David Phelps had to be taken out in the sixth inning of an 8-7 loss to the Orioles when an on-going right elbow issue flared up again.
Phelps, one of the club's key trade acquisitions in July, was taken out after facing three batters and will have an MRI exam when the club returns to Seattle for Thursday's off-day.
Phelps was making just his third appearance since returning from a 15-day stint on the disabled list from Aug. 8-23 due to an impingement in the elbow. The 30-year-old came into a 6-6 tie and gave up a single to Timothy Beckham and go-ahead sacrifice fly to Manny Machado before walking Jonathan Schoop.
After missing with a 90-mph cutter on ball four to Schoop, Phelps signaled to the bench and was taken out of the game after a brief talk with manager Scott Servais and athletic trainer Rick Griffin.
"In the bullpen, it's fine," Phelps said. "Playing catch, it hasn't bothered me. It's just when I get out there, that last curveball to Beckham when I really tried to get on top of it, it grabbed me a little bit. And same thing when I tried to go cutter in to Schoop, the last guy.
"This arm just doesn't want to get extended," he said. "It's frustrating. I'm out there trying to help the team win a ballgame and that happens."
Phelps was acquired from the Marlins in exchange for four Minor Leaguers on July 20. He's gone 2-1 with a 3.12 ERA in 8 2/3 innings over 10 relief appearances for the Mariners and has a 3.40 ERA in 54 outings on the season.

Phelps' departure was felt on a day Servais had to go to his bullpen early when starter Ariel Miranda gave up four homers and six runs in the first 4 1/3 innings. Rookie Emilio Pagan replaced Miranda for an inning, but he's been heavily used of late and the hope was to get four or five outs from Phelps to bridge the game to the late-inning crew.
Instead, Phelps could only get one out, and Servais had to call in Nick Vincent -- normally the eighth-inning setup man -- to quell a bases-loaded rally. Vincent pitched well again with four quick outs, but that left long reliever Christian Bergman pitching in the eighth, and he wound up taking the loss.
"Obviously he's a big part of our bullpen, trying to piece it together," Servais said. "And we've asked a lot of our bullpen, all these guys, stretching them and putting them in higher-leverage spots earlier in games sometimes. But today, it just didn't work out."
And that left Phelps frustrated on two levels as the Mariners headed back to Seattle lugging a five-game losing streak at the end of a tough 12-game road trip.
"Any loss is disappointing," Phelps said. "We're at the point of the season now where every game matters. This was one where we got out to a big lead and just didn't hold it. That's the most frustrating thing from a team standpoint. We need every win we can get, and we let one slip away."