NEW YORK -- Mets right-hander Tylor Megill left his start Thursday night against the Milwaukee Brewers with right shoulder discomfort, the latest setback in a promising season for the second-year pitcher.

And then, an inning later, Milwaukee suffered another potential blow to its depleted rotation, as left-hander Aaron Ashby exited his start with left forearm tightness. The team said he was removed as a precaution.

Megill came off the injured list last week after missing a month with right biceps inflammation. He will have an MRI on Friday, said the Mets, who went on to win 5-4.

"Pretty curious to see what it is," Megill said. "It's very strange. It's more so in the deceleration and not the actual throwing itself."

The rotation replacement for injured ace Jacob deGrom this season, Megill is 4-2 with a 5.01 ERA. He started for New York on Opening Day and pitched five scoreless innings in a win at the Washington Nationals.

Making his second start since returning from the injured list, Megill sailed through three shutout innings Thursday before Christian Yelich homered for the Brewers leading off the fourth. Milwaukee then loaded the bases with one out, and Megill winced immediately following his first pitch to Omar Narvaez.

"That's when I felt it more than before," Megill said. "I was just like, this is not worth it to keep throwing. Obviously wanted to."

It was the 28th pitch of a laborious inning for Megill, a fastball clocked at 92 mph -- well below the 97 mph he was hitting on the radar gun earlier in the game. He called for an athletic trainer and was replaced by Chasen Shreve.

"We're hoping to get lucky there," Mets manager Buck Showalter said.

Ashby gave up Mark Canha's two-run homer that tied the score at 4 in the fifth inning, then retired Brandon Nimmo on a grounder. That's when Brewers manager Craig Counsell, pitching coach Chris Hook and an athletic trainer went to the mound.

Following a discussion, Ashby walked off the field with the trainer and was replaced by Hoby Milner, who was given all the time he needed to warm up.

"Felt like I could've kept throwing," Ashby said. "It just crept up."

Ashby, the nephew of former major league pitcher Andy Ashby, is 1-5 with a 4.25 ERA in eight starts and six relief appearances this season, his second in the majors.

Before the game, Counsell acknowledged his preference would be to have Ashby in the bullpen at this stage were it not for injuries to All-Star starters Brandon Woodruff (right ankle, finger numbness) and Freddy Peralta (right shoulder).

"I'd say it's almost more fatigue than tightness," Counsell said of Ashby's ailment. "I think tomorrow will tell us a lot. I mean, the exam was good. But we'll see how he's doing tomorrow."

Megill spent four weeks on the IL from May 12 to June 9 with right biceps inflammation. He made one minor league rehab start and returned to the rotation last Friday at the Los Angeles Angels, allowing two runs and five hits on 64 pitches in 3⅓ innings.

Megill was 4-1 with a 2.43 ERA before getting tagged for eight runs and eight hits in 1⅓ innings May 11 at Washington. He was placed on the IL after that outing.

The Associated Press contributed to this report.