Washington Nationals pitcher Jon Lester will undergo surgery in New York to remove his thyroid gland, manager Dave Martinez announced Wednesday.

The Nationals were already made aware of his condition prior to giving him a one-year contract back in January. The team waited for results and Lester ultimately decided to remove the gland in the midst of Spring Training after consultation with the doctor.

“He said he felt kind of tired, that’s the big issue,” Martinez said. “I feel like once they get this out, he’ll have a lot more energy throughout the day. I hope it works out for him. I really do. He’s a big part of what we do here, and we love having him.”

Jon Lester was previously diagnosed with anaplastic large-cell lymphoma during his rookie season back in 2006 when he was playing with the Boston Red Sox. He eventually underwent chemotherapy and returned back to action almost 11 months after the procedure.

Lester was poised to get his first start in the Grapefruit League against the New York Mets on Wednesday morning. Due to his absence, right-handed pitcher Kyle Finnegan will slot in his position for the time being.

According to Martinez, the veteran is projected to make a return to practice a week after undergoing the operation in New York. Despite the situation, the Nationals are still expected to have Lester in their starting rotation to start this season.

“He’s been working his tail off, day in and day out, and I know he’s going to help us,” Martinez said. “So hopefully we can get this done, nip it in the bud and move on, and he’s back with us and in action soon.”

Once healthy, three-time World Series champion Jon Lester will definitely serve as an asset for the Nationals in their bid for a bounce-back campaign in 2021.