Washington Nationals pitcher Jon Lester is to undergo surgery to remove his thyroid gland but is expected to return in time for the Major League Baseball season, manager Dave Martinez said Wednesday.
Lester, who joined the Nationals on a one-year contract in January after ending his successful five-season stint with the Chicago Cubs, opted for surgery following a consultation on Tuesday.
The 37-year-old left-hander, a member of the Cubs' 2016 World Series-winning team, had complained of tiredness during pre-season training in Florida.
"He said he felt kind of tired, that's the big issue," Martinez was quoted as saying on the Nationals official website.
"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."
Lester was diagnosed with a form of non-Hodgkin's lymphoma in 2006 during his rookie season with the Boston Red Sox, and underwent chemotherapy before returning to baseball in 2007.
Martinez said Lester -- who had been due to face the New York Mets in a pre-season game on Thursday -- was expected to recover in time to make his first regular season start as planned.
"He has 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."