CLEVELAND -- Shane Bieber pitched until the pain stopped him.

Cleveland's ace will have season-ending Tommy John elbow surgery, a major blow to the Guardians and the 2020 Cy Young winner, who had looked like his dominant self in two strong starts to open the season.

Bieber, 28, struck out a majors-leading 20 and pitched 12 scoreless innings in starts against Oakland and Seattle despite the elbow getting progressively worse.

"Sheer toughness and grit," Guardians president of baseball operations Chris Antonetti said in describing how Bieber managed the pain and performed.

Bieber, who was limited to 21 starts a year ago due to elbow issues, experienced pain following his Opening Day start against the A's. The Guardians were concerned and gave him an extra day off while offering him additional treatment before facing the Mariners.

Bieber decided to make the start anyway, battling through six innings while the soreness and inflammation intensified.

He returned to Cleveland for more imaging tests and consultation. Dr. Keith Meister and Dr. Neal ElAttrache, the renowned orthopedist who did surgery on Browns quarterback Deshaun Watson's right shoulder, recommended elbow reconstruction.

Bieber made the decision to have the operation Friday night, knowing he will need up to 16 months to recover.

"He's devastated by it," Antonetti said on a Zoom call. "He feels as though he is letting a lot of people down. And I tried to reassure Shane that couldn't be further from the truth because he embodies what it means to be a professional, what it means to be a great teammate and a great leader."

Antonetti said Meister will perform Bieber's surgery in Dallas in the near future.

"He really put in a ton of work this winter and throughout spring training, and we all felt he was on a good path to stay healthy and contribute for the balance of the season," Antonetti said. "But ultimately when he got back into games and faced the stress of the major league environment, it just was too much for him."

Bieber is entering his final year under contract with the Guardians, who are off to a 6-2 start under first-year manager Stephen Vogt heading into Saturday's game in Minnesota.

Bieber is 62-32 with a 3.22 ERA in 134 career starts with Cleveland. He led the majors in wins, ERA and strikeouts in the pandemic-shortened 2020 season. Bieber made the All-Star team in 2019 and was named MVP when the Guardians hosted.

Bieber's injury is the latest for Cleveland's pitching staff. Reliever Trevor Stephan recently had Tommy John surgery and Gavin Williams has been sidelined since spring training with elbow soreness but should be fine.

The Guardians are hoping to contend in the American League Central and will need others to step up with Bieber no longer anchoring the staff.

"It's impossible to replace a pitcher and a teammate and a leader like Shane Bieber, so I don't think we have that expectation," Antonetti said. "Shane has been an incredible individual contributor and a great leader and presence on our team that has impacted the development of other people, so I wouldn't want to minimize the loss.

"At the same time, we are a resilient group and we found ways to overcome obstacles and injuries in the past, and I believe that the group that we have will be able to come together and find a way to help us continue to win games but it certainly will be harder to do without the health of Shane Bieber."