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ATLANTA — Frankie Montas’ first season with the Mets is over and his likely encore is in jeopardy.

The right-hander has been diagnosed with a “pretty significant” injury to the ulnar collateral ligament in his right elbow, according to manager Carlos Mendoza, and was placed on the injured list Saturday before the Mets faced the Braves at Truist Park.

Montas had soreness in his lower bicep on Friday, after warming up in the bullpen a day earlier in Washington — a game in which he didn’t pitch.

A subsequent MRI exam found the UCL damage.

Mendoza indicated that Tommy John surgery is a possibility for Montas.

The Mets signed Montas to a two-year contract worth $34 million last winter that includes an opt out.

But following a disappointing season in which he was demoted to the bullpen, Montas is sure to opt in for next season.

Huascar Brazobán was recalled from Triple-A Syracuse to take Montas’ roster spot.

Montas, 32, pitched this season to a 6.28 ERA in nine appearances, two of them in relief.

Montas opened the season on the IL after he was diagnosed with a high-grade lat strain in spring training.

He didn’t pitch his first game for the Mets until June 24.

“He was pretty devastated [Friday] when he found out, and rightfully so,” Mendoza said. “It’s been a hard year for him since spring training when he went down. He put in a lot of time rehabbing, came back and didn’t have the results.”

Brazobán has spent much of the season with the Mets, but was optioned to Triple-A Syracuse last month.

The right-hander, entering play, had pitched to a 3.83 ERA in 44 appearances for the club this season.

Brazobán will provide a length option from the bullpen, according to Mendoza.