SAN DIEGO -- Padres right-hander Mike Clevinger underwent Tommy John surgery on his right elbow and will miss the 2021 season, delivering an early blow to an upstart team with serious hopes of contending next year.

The club made the announcement on Monday, simultaneously noting that Clevinger has agreed to a two-year, $11.5 million contract which buys out his two remaining arbitration seasons.

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Clevinger, who sustained the injury in September with the Padres on the cusp of their first postseason berth in 14 years, underwent the operation on Tuesday in Cincinnati, tweeting a photo following the surgery.

The Padres had initially expressed optimism that Clevinger would avoid surgery. But general manager A.J. Preller noted that the injury persisted as Clevinger attempted his rehab plan. The pitcher was examined by at least four elbow specialists -- multiple times each -- before he ultimately settled on surgery.

"Everybody was in agreement that, rather than try and piece it together and get through the next season, I think he felt like, 'I want to go ahead and get this taken care of, have the procedure, and push toward the 2022 season,'" Preller said. "We were optimistic at various points in time in the process, especially earlier in the process when the season ended. As we went through the rehab process the last few weeks and he wasn't getting drastically better, he felt like the surgery was the best route."

When the Padres landed Clevinger 2 1/2 months ago, it was quite the splash. The 29-year-old arrived from Cleveland in a nine-player blockbuster as a central tenet of Preller's long-term vision. The Padres had built a young team ready to contend, so they supplemented it with an ace.

The most exciting part for the Padres? Clevinger was under team control through 2022.

"When we made the trade, we made the trade with three pennant races in mind," Preller said.

Now, it looks like the Padres will get a combined total of one postseason inning from Clevinger in the first two of those seasons.

Clevinger initially sustained the injury in September, though the timeline for his progression to Tommy John surgery remains strangely foggy. He made four starts for the Padres and posted a 2.84 ERA. But in his third outing -- a seven-inning shutout against the Giants -- his elbow barked during his last inning.

Clevinger was scratched from his next start, then he pitched just one inning in his final outing against the Angels because the injury flared up again. He was diagnosed with a right elbow impingement at the time.

The Padres and Clevinger did everything they could to get him healthy in time for the postseason. Clevinger was given a cortisone injection immediately following the regular season, and he returned to start Game 1 of the National League Division Series against the Dodgers.

In retrospect, that decision was probably ill-advised. There will be lingering questions as to whether Clevinger’s attempted October return negatively impacted his health. But Preller reiterated that he believes Clevinger's playoff start did little to exacerbate the injury.

"He felt he was going to be able to perform," Preller said. "Our medical teams did. We put him out there and ultimately, he ended up coming off the field, walking off the mound. ... My guess is it was something in there when he went and took the mound that was going to happen at some point, had probably already happened [against the Giants on Sept. 13]."

Now the Padres are left without one of their two aces in 2021, though Preller expressed optimism that Dinelson Lamet -- who also sustained a September elbow injury -- wouldn't reverse course in his recovery the same way Clevinger did. The Padres still expect Lamet to be fully healthy for Spring Training, Preller added.

“Whereas Mike, the last couple weeks, just could never really get over that hump, with Dinelson, he’s feeling great,” Preller said. “Looks like he’ll be able to start his normal throwing program on Dec. 1, which is normal for him every year. He’s in a good place right now.”

Clevinger is expected back for the 2022 season, and his contract extension ensures he will remain in San Diego for it. Clevinger will make $2 million in '21 and $6.5 million in '22 with a $3 million deferred signing bonus, according to sources. He also has performance-related bonuses for '22.

"He fell in love with the city and the team, and he wants to be here," Preller said. "Everybody looked at it and from a common-sense standpoint: This is what's important to the Padres, this is what's important to Mike, and we wind up on a two-year deal."

• How will Padres replace Clevinger in '21?

The contract gives the Padres some financial flexibility this winter, as Clevinger would have received more than twice his 2021 salary in arbitration. When he returns for '22, San Diego could be set up to have one of the sport's most fearsome rotations -- led by Clevinger, Lamet and Chris Paddack, with top pitching prospects MacKenzie Gore, Luis Patiño and Ryan Weathers potentially making an impact.

That said, it’s a near certainty that the Padres will add to their rotation mix this winter. That much was true whether Clevinger was going to be available for 2021 or not.

"It doesn't change it a ton," Preller said. "We looked at it knowing that in Mike's situation, even if the reports from the doctors were coming back positive … until you get out there on the mound, it's a little tough to [know].

"We've been looking at it like: You never have enough starting pitching because of injuries and because of situations like this."