New York Mets ace Kodai Senga has a moderate capsule strain in the back of his right shoulder and is expected to begin the season on the injured list, president of baseball operations David Stearns said Thursday.

Senga underwent an MRI after he experienced arm fatigue after throwing a side session during spring training.

Stearns said that Senga will be shut down until his symptoms subside and strength returns to his shoulder in normal levels.

"We don't expect him to be ready for Opening Day, so at this point we would expect him to begin the season on the IL," Stearns said.

He added that he doesn't know at this time how long Senga will be sidelined, but it's not an injury that will require surgery. Instead, it will be treated with rest, treatment and maybe an injection.

"What I can say at this point comfortably is that we don't expect Opening Day, but I do expect him to make a bunch of starts this year," Stearns said.

Senga, speaking through an interpreter, said he can still throw 96 to 98 mph with the injury, "but the game isn't about throwing fast, it's about getting hitters out."

He added, "At this point, I'm not going to be able to perform at the highest level, so giving it a little bit of time is the right move."

New York is looking to Senga to help anchor its rotation after he put together an impressive rookie season. The Mets also signed right-hander Luis Severino and left-hander Sean Manaea in the offseason, and they acquired right-hander Adrian Houser in a December trade with the Milwaukee Brewers.

Stearns said he doesn't expect to add a pitcher from outside the organization to fill the void left by Senga while he is sidelined.

"It is regretful that I'm not about to be a part of [the rotation] at the beginning of the season, but I think I just have to be positive and look forward to being back out there with the team," Senga said.

Senga, 31, signed a $75 million, five-year contract with New York in December 2022. He went 12-7 with a 2.98 ERA in 29 starts last year.

The Mets are hoping to rebound after they finished fourth in the National League East with a 75-87 record in 2023. Stearns took over as president of baseball operations in September, and manager Carlos Mendoza was hired in November.

The Associated Press contributed to this report.