MILWAUKEE -- Frankie Montas has not pitched to expectations since being acquired by the Yankees prior to the Aug. 2 Trade Deadline, and now, the right-hander is set to undergo an MRI after experiencing discomfort in his pitching shoulder following New York's 7-6 loss to the Brewers on Friday.

Montas missed time earlier this season with a similar issue while pitching for the A's, exiting a July 3 start and returning on July 21. Staked to a five-run lead on Friday, Montas lasted only 3 1/3 innings, allowing four runs.

“I’m at least a little bit concerned,” Yankees manager Aaron Boone said. “It seems to be less than what he was dealing with when he was in Oakland a couple of months ago. Obviously, we’ll know more when we get this [MRI] and then they can move forward from there.”

In eight starts as a Yankee, the 29-year-old Montas is 1-3 with a 6.35 ERA, permitting 28 runs and 46 hits over 39 2/3 innings. He is 5-12 with a 4.05 ERA in 27 starts this season overall.

“I think it could have had something to do with last night, but as far as I know, he’s been good and healthy,” Boone said. “Even last night, according to him, it was fairly minor. But we’ll see.”

Boone had said that he planned to have Montas remain in the rotation to face the Red Sox next week. That is now in flux, pending the results of Montas’ MRI and an evaluation to follow in New York, where Montas will be examined by team physician Christopher Ahmad.

If Montas cannot make his start as scheduled, Boone said that Domingo Germán would likely return to the rotation. Germán has been used as an opener and long reliever since his last multi-inning start on Sept. 7. Luis Severino is also scheduled to return from his Minor League rehab assignment for a Wednesday start against the Pirates.

The Bombers’ moves at the Trade Deadline have largely not worked out thus far. In addition to Montas’ inconsistency, outfielder Andrew Benintendi’s return date is unknown from a hand injury, right-hander Scott Effross has been on the injured list and outfielder Harrison Bader has yet to make his debut due to plantar fasciitis.

The outlier is right-hander Lou Trivino, who was included in the Montas trade with Oakland and has pitched to a 1.13 ERA in 19 appearances with New York. 

“Even as we’ve started to play well here, we’re still beat up and banged up,” Boone said. “But we’re also excited about the possible returns of some key guys.”