NEW YORK — In building their 2025 rotation, the Mets bet on upside.

They re-signed Sean Manaea, who, with a lowered arm slot, delivered a career-best season in 2024.

They added Frankie Montas, whose mid-90s fastball and swing-and-miss splitter headline one of the nastiest repertoires in baseball.

They signed Clay Holmes, believing the two-time All-Star reliever’s untapped arsenal will allow him to transition to the starting rotation.

And they’re excited about Kodai Senga, who missed all but one start last season due to shoulder and calf strains.

“This rotation has the potential to pretty much throw, I would say, five No. 1s, every five days,” Montas said last weekend during the Amazin’ Day fan festival at Citi Field.

Of course, there are question marks.

Montas, 31, is three years removed from a 2021 season in which he finished sixth in American League Cy Young Award voting with the Oakland A’s.

He is 12-23 with a 4.45 ERA over the past three seasons with the A’s, Yankees, Cincinnati Reds and Milwaukee Brewers, and he missed nearly all of 2023 after undergoing right shoulder surgery.

Last year, Montas pitched to a 4.84 ERA with 148 strikeouts over 150.2 innings with the Reds and Brewers.

He signed a two-year, $34 million contract with the Mets in December.

Holmes, 31, posted a 2.69 ERA over parts of four seasons with the Yankees from 2021-24, exclusively as a reliever, but he has started only four of his 311 career MLB appearances.

The right-hander, who signed a three-year, $39 million deal, leaned on a power sinker and a slider out of the bullpen. He is working this winter on incorporating a changeup, while his four-seamer served him well as he threw it more last postseason.

Short-term signings paid off for the Mets last year, when they got a 3.47 ERA over 181.2 innings from Manaea and a 3.91 ERA over 182 innings from Luis Severino, who has since left for the A’s.

Montas and Holmes both cited the successes of Manaea and Severino among the reasons why they signed with the Mets.

The Japanese-born Senga, meanwhile, dominated in 2023 during his first MLB season, pitching to a 2.98 ERA and 202 strikeouts over 166.1 innings, but he missed the first four months of last season after being diagnosed in spring training with a shoulder injury.