Nationals manager Dave Martinez made the announcement Wednesday and also said Lester is expected to return to camp within five to seven days. According to Martinez, this should not affect Lester's roster status for Opening Day, assuming the procedure and recovery go as planned.
Some additional context from Mark Zuckerman:
Jon Lester, as many know, was diagnosed with lymphoma in '06. Went through chemotherapy, returned to pitch for Red Sox in July '07, has been healthy ever since. Reported to Nats coaches/doctors this spring he was feeling tired. Thyroid issue discovered, he'll now have it removed.— Mark Zuckerman (@MarkZuckerman) March 3, 2021
Lester, 37, is coming off an abbreviated 2020 season with the Cubs in which he pitched to a 5.16 ERA and 2.47 K/BB ratio in 12 starts. For his career, Lester owns an ERA+ of 119 and a WAR of 45 across parts of 15 big league seasons. He enters the 2021 season with 193 career wins.
Lester signed a one-year, $5 million contract with the Nationals this winter after spending the last six seasons with the Cubs. In Washington, he's expected to slot in the rotation behind Max Scherzer, Patrick Corbin, and Stephen Strasburg.