The New York Yankees may have lost their biggest offseason acquisition before Spring Training even starts. Right-hander Frankie Montas, who was expected to be a big part of the team's rotation this year, will undergo shoulder surgery that could cause him to miss the entire season, manager Aaron Boone announced on Wednesday.

Montas will undergo arthroscopic surgery on his shoulder on Feb. 21, with a best-case scenario for a return not until late in the 2023 season.

The 29-year-old was already known to be behind schedule heading into Spring Training, due to inflammation in his right shoulder that slowed his offseason progression. Yankees' general manager Brian Cashman said weeks ago that the damage didn't appear to be structural in nature.

Cashman said more information would be gained once Montas began his throwing program. That was scheduled for late January, and it seems clear that things did not quite go as planned for Montas and the Yankees.

Montas, who turns 30 in March, was 5-12 with a 4.05 ERA in 27 starts for the Oakland Athletics and Yankees last season.

The Dominican Republic native was acquired from the A's alongside reliever Lou Trivino last summer in a deadline deal that sent prospects Ken Waldichuk, JP Sears, Luis Medina and Cooper Bowman to Oakland.

Montas had been excellent before the trade, pitching to a 3.30 ERA over 291 innings dating back to 2021 Opening Day. But he struggled in the pinstripes, yielding six runs in two of his first three appearances and four or more runs in eight Yankees starts before landing on the injured list.

Frankie Montas and the New York Yankees avoided arbitration this offseason; he is on a one-year, $7.5 million deal for the 2023 season, and will be a free agent in the offseason.

New York’s current rotation projects to feature Gerrit Cole, Carlos Rodón, Luis Severino and Nestor Cortes, with Domingo Germán and Clarke Schmidt among those battling for the No. 5 spot.