ATLANTA — Despite getting roughed up throughout his rehab assignment, Mets right-hander Frankie Montas is expected to join the club’s rotation next week and make his team debut in New York’s series against Atlanta.

Montas has been out since before the Grapefruit League season even started in spring training with a right lat strain. His rehab assignment, which began in late May, did not go smoothly. In six starts between High A and Triple A, Montas allowed 25 earned runs and 42 baserunners in 18 2/3 innings. He struck out 12 compared to 10 walks.

His struggles during the rehab assignment prompted the Mets to consider bringing him back as a reliever. After all, New York’s rotation has been one of the very best in the sport all season. However, recent injuries to Kodai Senga and Tylor Megill have opened up a pressing need in the rotation.

The Mets are planning to fill Megill’s spot Friday with Justin Hagenman, who has one career major-league appearance, from earlier this season. That’s the spot Montas will likely step into next week.

“We need starters here,” manager Carlos Mendoza said. “We signed him to be a starter.”

The Mets have been working on a mechanical issue with Montas’ upper-body rotation through his delivery. Even if the team wanted to keep Montas in the minors to work through these issues, though, the pitcher’s rehab clock expires on Sunday. Extending it would require approval of an injury from MLB and from Montas personally. Montas said last week at Citi Field that he feels healthy.

While Mendoza didn’t sugarcoat how the rehab assignment went, he compared it to spring training for the veteran, who didn’t get to build up at all back in February and March.

“I’m not going to lie, he got hit around,” Mendoza said. “We’ve seen it before with guys in spring training getting hit around and once you put them in a big-league game under the lights, they flip the switch.”

And Montas has been a poor spring training performer over the last few seasons. From 2021 to 2024, Montas has pitched to a 6.23 ERA in the spring — and a 4.02 mark in the regular season. (For his career, Montas’ 4.08 spring ERA is remarkably close to his 4.09 regular-season ERA.)

Last season, he posted a 4.84 ERA between stints with the Reds and the Brewers. New York was encouraged by some of the changes Milwaukee made with Montas down the stretch, which compelled it to make a two-year $34 million investment in the 32-year-old.

(Photo: Sam Navarro / Imagn Images)