Dodgers right-hander Tony Gonsolin will undergo Tommy John surgery to repair a torn ulnar collateral ligament in his elbow Friday, a procedure that will sideline him for all of 2024.

Gonsolin, 29, was placed on the 15-day injured list because of right forearm inflammation on Aug. 19, one night after he gave up a career-high 10 earned runs and five homers in 3 1/3 innings of an 11-3 loss to Miami that dropped him to 8-5 with a 4.98 ERA in 20 starts on the season.

An MRI test confirmed what the Dodgers had known for weeks — that Gonsolin was pitching with a UCL tear, an injury both the pitcher and the team felt Gonsolin could manage until that dreadful start against the Marlins.

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“We knew he was dealing with some elbow issues, but there was a point where he felt like he could pitch and get major league hitters out … until he couldn’t,” manager Dave Roberts said before Monday night’s game against the Arizona Diamondbacks. “Talking to the doctors, we just felt that it was time. I guess at some point it was inevitable.”

Gonsolin missed the final five weeks of the 2022 season because of a right forearm strain and the first four weeks of 2023 because of a left ankle sprain suffered in spring training.

He returned in late April but never regained his 2022 All-Star form, muddling his way through the season with a diminished fastball and a four-pitch mix that wasn’t nearly as crisp as it was last season, when Gonsolin went 16-1 with a 2.14 ERA in 24 starts.

Roberts had made vague references to Gonsolin “not being 100%” for several weeks, but the Dodgers thought Gonsolin turned a corner with an Aug. 12 start against Colorado, when he responded to a first-pitch homer by Ezequiel Tovar to throw six two-hit, shutout innings with six strikeouts and no walks in a 4-1 win.

It wasn’t until Gonsolin was shelled by the Marlins in his next start that Roberts acknowledged for the first time publicly that Gonsolin had been dealing with an “arm issue” for four to six weeks. The manager said after that game that the team’s medical staff assured him Gonsolin would not do any further damage by continuing to pitch, and Roberts maintained that stance on Monday, despite what seemed like a dramatic turn for the worse for Gonsolin.

“He didn’t tear it further,” Roberts said. “He was pitching, and it was asymptomatic. He felt like he could keep pitching, and to be quite honest, he can still pitch right now. But it just wasn’t productive.

“Pitchers always have some damage or tears. Some guys can pitch through it, and Tony did. There was nothing an MRI showed after his last start that was worse, that caused the surgery. We thought this was a potential [outcome] from the middle of the season."

There was substantial financial incentive for Gonsolin, who avoided arbitration by signing a two-year, $6.65-million contract last winter, to pitch through discomfort.

Gonsolin’s contract includes incentives that increase his 2024 salary of $3.4 million based on points earned in 2023, with one point per start and one point per relief appearance of 3 1/3 innings or more, and $500,000 awarded for each of 14, 16, 18, 20, 24 and 28 points.

With the 20 points he accrued with 20 starts, Gonsolin boosted his 2024 salary by $2 million, from $3.4 million to $5.4 million.

But could Gonsolin’s desire to pad his guaranteed salary for 2024 and fill a spot in the team’s injury-ravaged rotation have caused him to push his elbow too far?

“I think that was a motivation to pitch, and I can sympathize and understand that from the player’s perspective,” Roberts said. “I still believe that if we would have stopped this process months ago, he would be in the same position. We had a really honest conversation with Tony knowing that surgery was the ultimate potential outcome.

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“But I appreciate him wanting to keep pitching, and to be quite honest, where we were at with our pitching staff at that point in time, we were running through some guys, and he felt he wanted to keep pitching because he felt he could help his ballclub. So it went both ways.”

The velocity of Gonsolin’s four-seam fastball has dropped steadily over the last three seasons, from an average of 95.1 mph in 2020 to 93.8 mph in 2021, 93.1 mph in 2022 and 92.4 mph in 2023.

Gonsolin said the injury impacted his stuff more than command. Roberts said it was difficult to determine how much of Gonsolin’s struggles were performance-related or injury-related. Asked if Gonsolin’s discomfort was what a starting pitcher would normally feel 15 to 20 starts into a season, Roberts said, “I wouldn’t say that. I would say he felt good enough to pitch, where somebody else could have the same imaging and not be able to pitch.

“There were still some 93’s and 94’s, the slider was good. He just wasn’t getting guys out. We felt he’s earned the opportunity to try to work through it, he’s earned the opportunity to try to reach some incentives. And at some point, we talked and said that this was good enough, and we both agreed.”

Gonsolin is the third Dodgers starting pitcher to undergo Tommy John surgery since July 2022, joining Dustin May and Walker Buehler.

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This story originally appeared in Los Angeles Times.