NEW YORK — The New York Mets’ sputtering rotation was dealt another setback this week when Sean Manaea, rehabbing from an oblique injury sustained during spring training, was diagnosed with a loose body in his left elbow.

Mets manager Carlos Mendoza said Tuesday that Manaea reported elbow discomfort after his most recent rehab start for Triple-A Syracuse last Thursday. He received a cortisone shot Monday and was shut down from throwing for 48 to 72 hours.

Mets president of baseball operations David Stearns said Tuesday the discovery should not delay Manaea’s return for long. He said the goal is for Manaea to make his final rehab start next Tuesday or Wednesday before joining the Mets’ rotation for his season debut.

“I’m just very thankful it wasn’t nothing very serious,” Manaea, 33, said Tuesday. “So, it’s kind of a silver lining. It sucks, but it’s a pretty good case scenario for what it is.”

Manaea, who re-signed with the Mets for three years and $75 million during the winter after serving as the team’s ace in 2024, initially strained his oblique in late February. He began throwing in mid-March but experienced a setback two weeks later. The Mets estimated late May as his earliest possible return date, but Manaea didn’t begin his rehab assignment until June 6.

He made three starts for High-A Brooklyn, allowing eight runs across 6⅔ innings, before starting for Syracuse last week. Manaea allowed one run on two hits with seven strikeouts and no walks across 5⅓ innings, stretching his workload to 62 pitches.

Manaea said he began feeling soreness late in the outing. He assumed the irritation was normal until the next day when it did not diminish.

“I don’t really have any frame of reference,” Manaea said. “Never dealt with anything like this before. It’s definitely something new for me. I hope I’m not grinding every single outing, but I think that’s the hope, this thing kind of subsides and I’m able to pitch through it.”

Both Stearns and Mendoza said that surgery to remove the loose body is currently not on the table for Manaea, though Stearns and Manaea acknowledged it’s a possibility after the season. Manaea said he was told pitching with the loose body should not cause ligament damage.

“I think that is to be determined,” Stearns said of a procedure to remove the loose body. “Sometimes you can pitch with these loose bodies for your entire career. And sometimes they need to come out so I don’t know if we have a definitive determination on that.”

For now, the Mets appear to have avoided a severe blow for a rotation that has encountered a rough June featuring considerable regression and injuries to Kodai Senga (hamstring) and Tylor Megill (elbow). The Mets entered June with a 2.89 ERA, good for second across the majors. This month, the group has compiled a 3.96 ERA, which ranks 12th.

The combination of injuries, decline and the offense’s significant struggles had produced nine losses in 10 games entering Frankie Montas’ Mets debut Tuesday against the Atlanta Braves. Montas was making his first start since signing a two-year, $34 million contract over the offseason after an ugly rehab assignment in which he posted a 12.05 ERA in 18⅔ innings across six starts.

But the right-hander was effective in his season debut, throwing five shutout innings. He struck out five — including Braves star Ronald Acuña Jr. twice on 96 mph heaters.

Montas was removed with a 3-0 lead after 80 pitches on a 97-degree night at Citi Field, but New York’s bullpen promptly gave up five runs in the sixth en route to a 7-4 defeat.

The Mets hope Manaea will return shortly after to stabilize a rotation that has been teetering in recent weeks.

“It’s not fun,” Manaea said. “I wish to be out there very bad.”

Information from The Associated Press was included in this report.