HOUSTON – The A’s were hopeful that Ken Waldichuk would be able to boost their starting rotation at some point in 2024. Now, they’ll have to plan for the rest of the season without the left-hander.

Waldichuk underwent Tommy John surgery on Wednesday in Los Angeles with Dr. Neal ElAttrache. The procedure was a flexor tendon repair and a full reconstruction of the ulnar collateral ligament in his pitching elbow. Waldichuk also had an internal brace procedure, which many notable pitchers have recently undergone, including Braves right-hander Spencer Strider in April. He will miss the remainder of the 2024 season, and the A’s estimate a recovery in the range of 13 months, putting him in line to potentially return to Major League action as soon as June 2025.

“I know he’s got to be frustrated to have a setback and have to go through surgery,” manager Mark Kotsay said ahead of Thursday’s series finale against the Astros at Minute Maid Park. “But it’s what’s best for him and his career. We’ll get him back, hopefully, in 13 months. A lot of guys have come back from this procedure even better, so there’s a positive to that as well.”

Following his final start of the 2023 season last September, Waldichuk experienced discomfort in his left elbow and was eventually seen in October by ElAttrache, who diagnosed him with a flexor tendon strain and UCL sprain. At the time, Waldichuk opted for conservative treatment, undergoing a Tenex procedure with Dr. Steve Yoon on Oct. 17 and receiving a follow-up PRP injection to the flexor tendon a week later.

Waldichuk rehabbed throughout the offseason and into Spring Training. Around the first week of April, he began throwing bullpen sessions and even progressed to facing hitters in live batting practice sessions. He was considered near ready to begin a rehab assignment in the Minors, but after a setback following his live batting practice session on April 29 at the Coliseum, Waldichuk was shut down from throwing.

“The PRP and Tenex procedure both did their job up until Ken had to put more effort into it in the live BP,” said A’s director of sports medicine and rehabilitation Brian Schulman. “His elbow couldn’t withstand the demands needed to throw at the Major League level. … I can sympathize with Ken in that you’re not just going to say, ‘Yes, just cut me open and let’s get this over with.’ There was a chance he could [get through it without surgery], and that’s what Ken opted to do.”

Entering last season rated as Oakland’s top overall pitching prospect, Waldichuk endured some first-half struggles, though the A’s were excited by a strong finish that saw him post a 3.83 ERA in his final 11 games (nine starts) after a temporary move to the bullpen helped him reshape his mentality on the mound and refine his arsenal of pitches.

Waldichuk’s surgery piles on to a rough stretch for the A’s in the pitching department. Over the past week three members of their Opening Day starting rotation -- Joe Boyle, Paul Blackburn and Alex Wood -- have landed on the injured list.

“There are decisions in front of us that we’re still discussing in terms of how to fill those spots,” Kotsay said. “It’s unfortunate because we had a good rhythm going with those starters and our bullpen. But that’s part of the season. It’s part of the grind we go through. The mindset has to be that the next guy up has to do his job.”

There is some optimism for another injured pitcher, Luis Medina. Out since early Spring Training with a Grade 2 MCL sprain, the 25-year-old hard-throwing righty has been progressing well in his rehab. He threw 43 pitches in the Arizona Complex League on Wednesday, with his fastball sitting around 97 mph and maxing out at 100 mph. Medina will join Triple-A Las Vegas to continue building up as a starter and is expected to be ready for his season debut once he’s eligible to come off the IL on May 27.

“The progress that he’s making is great,” Kotsay said of Medina. “That’s encouraging. You leave Spring Training feeling like you have depth, and we’re definitely tapping into all the depth that we have.”