It’s not even March and the Mets already have a health concern with their best starting pitcher.

Kodai Senga experienced arm fatigue after his Tuesday side session, manager Carlos Mendoza told reporters Wednesday, and was being examined by the training staff.

“He got on the mound yesterday, and today he came in and, just overall arm fatigue,” Mendoza said.

Any issues with Senga’s arm bear watching, as any sort of injury absence would be a major blow to the Mets’ rotation.

After arriving from Japan on a five-year, $75 million contract last year, the 31-year-old right-hander, known for his “ghost” forkball, was an All-Star in 2023 with a 2.98 ERA and 202 strikeouts in 166 ⅓ innings.

The Mets, who traded future Hall of Famers Max Scherzer and Justin Verlander during the team’s disappointing 2023 season, added Luis Severino and Sean Manaea in free agency and Adrian Houser in a trade.

Veteran left-hander Jose Quintana returns and right-hander Tylor Megill is another rotation option.