Zach Eflin’s 2021 season is finished, and it has the Phillies rethinking the way they will approach the offseason.

The Phillies announced on Tuesday that Eflin will have surgery on Friday in Philadelphia to repair a tear in his right patellar tendon. It will be the second surgery on Eflin’s right knee in five years. He had surgery to repair the patellar tendon in his right knee on Aug. 19, 2016, and the patellar tendon in his left knee on Sept. 30, 2016. He rejoined the Phillies rotation in mid-April 2017, less than seven months after the left-knee surgery. The Phillies estimate Eflin’s recovery this time to be anywhere from six to eight months, which means he theoretically could be pitching again as early as March 2022.

Of course, Eflin had those first surgeries when he was 22. He will have the second surgery on his right knee at 27.

“Well, sure, there’s a concern,” Phillies president of baseball operations Dave Dombrowski said at American Family Field. “Nobody has said that his career is threatened, but sure, it’s a concern. There’s a key guy for us that you’re talking about being out 6-8 months. It’s a long time and it’s a major surgery.”

Eflin was 4-6 with a 3.88 ERA in his first 17 starts this season before he allowed six runs in 3 2/3 innings against the Marlins on July 16. The Phillies scratched him from his next start, citing tendinitis in his right knee. The club and Eflin said then that they hoped he might only miss one turn through the rotation, but his knee never improved.

He began a slow recovery, which included PRP injections into the knee. There seemed to be some progress because he had been scheduled to rejoin the rotation on Aug. 26 against Arizona at Citizens Bank Park. The Phillies activated him from the 10-day injured list, but when he showed up at the ballpark that afternoon, the knee flared up. He could not pitch. The Phillies planned to return him to the 10-day IL, but he tested positive for COVID-19 (Eflin is vaccinated) and landed on the COVID-19 IL instead.

Because he had COVID, he could not see Phillies physicians or athletic trainers until he got cleared. He finally saw doctors on Monday.

“When he went in there to get checked by the doctors, the tear itself, which they were treating with some PRP injections, had not improved,” Dombrowski said. “That’s how they were hoping to treat it. The hope was that he’d be able to get through it with just the PRP injections, which works on a lot of things, but they came to the conclusion when they saw him yesterday that it hadn’t healed in a significant enough fashion. So the thought was then, let’s do the surgery now.”

It might change the Phillies’ wintertime plans. When the club acquired Kyle Gibson from the Rangers on July 30 and moved Ranger Suárez from the bullpen to the rotation in a subsequent move, they figured they had the makings of their 2022 rotation with Zack Wheeler, Aaron Nola, Eflin, Gibson and Suárez.

But now that Eflin, who is eligible for salary arbitration for a third and final time this offseason, is sidelined possibly into May -- the Phillies acknowledge they will not have a clear picture about his recovery until probably mid-November -- they will have to consider starting pitching options.

“Yeah, it changes our thought process for sure because I really didn’t think we’d have to talk about starting pitching because I thought we would be set,” Dombrowski said. “But we’ll have to talk about that in addition to whatever else we want to address.”

Internally, left-hander Bailey Falter is an option. The Phillies planned to have him start this summer until he tested positive for COVID-19. The Phillies just promoted right-hander Hans Crouse from Double-A Reading to Triple-A Lehigh Valley. They acquired him from the Rangers. He must be placed on the 40-man roster in the offseason.

“He’s pitched very well,” Dombrowski said. “He throws multiple pitches. His delivery is different. He’s more of a max effort delivery, I guess, so that’s why a lot of people say maybe a reliever, but he also commands his pitches, so he throws them very well. He doesn’t walk many people. He has command of the strike zone. I’m sure we’ll have a lot of future discussions on this. It’s just not the time right now for that.”

The Phillies plan to use their bullpen every fifth day the rest of the season in Eflin’s absence.