With fellow lefty Charlie Furbush on the disabled list, veteran Mark Lowe traded to Toronto on July 31 and several other relievers struggling, the Mariners leaned on Beimel more heavily than they wanted in recent weeks. And the result may have the 13-year veteran headed to the DL himself.
"I've been kind of fatigued the last week or so," Beimel said. "It's kind of like I was throwing through mud. Everything was real slow and I wasn't bouncing back. I thought I'd be able to just kind of fight through it and keep going out and battling and getting through it.
"But today was just one of those things where I don't think I'm going to be able to do that anymore. So I think we're going to see how it feels [Friday] after the off-day and go from there. I don't really know what to tell you, other than that."
Manager Lloyd McClendon knows something isn't right with Beimel, whose ERA has jumped from 2.50 to 4.78 over his last five outings.
"I'm concerned," McClendon said. "I'm concerned about his health. I need to talk to him and make sure he's where he needs to be. Until I do that, I won't be convinced. The workload has been such that none of those guys are 100 percent. I've tried to give him a few days off so he could come back, but he's been elevating a lot of pitches."
Beimel said every pitcher gets taxed during the long season, so he kept taking the ball when asked.
"It's definitely tired," he said of his arm. "Today was a little different kind of tired. I felt it grabbing a little in the back. I don't know if that's just a knot back there or what, but we were kind of digging around on it afterward and could feel some knots in there. We'll see."
Beimel didn't pitch in the Majors in 2012 or '13 as he returned from Tommy John surgery, then was one of the better comeback stories in baseball when he posted a 2.20 ERA in 45 innings over 56 appearances last year for Seattle.
Despite pitching the first month of this season in the Minors after signing back with the Mariners at the end of Spring Training, Beimel has already thrown 37 2/3 innings in 42 outings with seven weeks remaining.
Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB, read his Mariners Musings blog, and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.