New York Mets righty Kodai Senga has arm fatigue and is being assessed by trainers, manager Carlos Mendoza said Wednesday.

Senga first felt something was off while throwing a side session on Tuesday, though no MRI is currently scheduled. This is his second season in Flushing after 11 with Japan’s Fukuoka Softbank Hawks. Senga brought his legendary “ghost” forkball to MLB and posted a 2.98 ERA in 19 starts. Not bad for a 30-year-old “rookie.”

Unfortunately for the Mets, losing Kodai Senga for an extended period of time could prove devastating. All signs pointed to him being the Mets’ ace this year. The Mets did well to add some depth behind him, namely free agent signees Luis Severino and Sean Manaea.

It’s also early enough in spring training that, knock on wood, Senga can recover with simple rest and rehab. The Mets need his strikeouts after he fanned 202 hitters in just 166.1 innings last season.

“After his side session yesterday, he came in and experienced some arm fatigue,” said Mendoza. “So he stayed inside and we’re taking a look at it.”

Stay tuned to ESNY for more updates out of Mets spring training.