"The last couple times out, I just really haven't gotten loose like I have in the past," Phelps said. "As far as getting loose in the bullpen it's been fine, but I get in the game and it's still tight. I can tell the ball just isn't coming out, and my stuff hasn't really been the same.
"In the past, I've pitched through things and broken my arm, so I thought it was better to let them come out. The training staff has known about it and I've been getting treatment, but I'll go see the doc and see what he has to say."
Phelps spent time on the disabled list in 2013 with a strained forearm, in '14 with shoulder inflammation, in '15 with a stress fracture in his forearm and last year with a strained oblique. Manager Scott Servais said Phelps could be headed to the DL, at least for a short stint now, depending on what the doctors see.
"I've had a litany of elbow injuries, things that have forced me to not throw," Phelps said. "But I've been playing catch and warming up in the bullpen. My command is still there, it's just a matter of the ball isn't coming out the way I want it to, and where we're at as a team right now, I figure it's better to nip it in the bud then try to go out and be a hero and cost us some games."
After retiring Butera, Phelps immediately signaled to the Mariners' dugout. Servais and athletic trainer Rick Griffin spoke briefly to Phelps before he left the mound, shaking his head.
"There's radar guns all over the stadium and I looked out and I'm throwing 90 mph, and I know the ball's not coming out," said Phelps, who normally throws in the 95-mph range. "That last pitch, I said I'm going to stand on this one a little bit [when he hit 93] and it's that extension when I felt it."
Phelps was acquired from the Marlins in exchange for four Minor Leaguers on July 20. He has posted a 2.57 ERA in seven innings over seven appearances, while providing another solid right-handed setup man to a Mariners bullpen that has the lowest ERA in the Majors over the past 66 games. For the season, the 30-year-old is 3-5 with a 3.35 ERA in 50 games with the Marlins and Mariners.
Greg Johns has covered the Mariners since 1997, and for MLB.com since 2011. Follow him on Twitter @GregJohnsMLB. This story was not subject to the approval of Major League Baseball or its clubs.