Philadelphia Phillies ace Zack Wheeler’s season is over after being diagnosed with thoracic outlet syndrome, the team announced on Saturday.

The 35-year-old right-hander will require decompression surgery in the coming weeks and is expected to miss six to eight months. The procedure threatens his ability to be ready for the start of the 2026 campaign.

Wheeler recently underwent surgery to remove a blood clot from his upper right arm. A second opinion recommended further intervention. Thoracic outlet syndrome occurs when bones or muscle press on blood vessels in the upper chest, causing pain or numbness.

“It’s disappointing, but everybody knows it’s out of our control,” said Phillies manager Rob Thomson. “We’re happy he’s going to be healthy, because it’s a very serious thing that he went through.”

Wheeler had reported “heaviness” in his shoulder after his 15 August start in Washington, prompting the Nationals’ team doctors to examine him and discover the clot. Phillies head athletic trainer Paul Buchheit said the issue was unrelated to Wheeler’s earlier shoulder soreness.

Buchheit added that Wheeler could begin a throwing programme about eight weeks after surgery, though the precise timeline remains unclear. “I’m glad he’s OK and the prognosis is he’ll be back relatively soon in the [2026] season,” said Dave Dombrowski, the club’s president of baseball operations.

Wheeler was 10-5 with a 2.71 ERA across 24 starts and 149 and two-thirds innings this season. His 195 strikeouts lead the National League and he was widely considered a Cy Young Award contender. A two-time runner-up for the award, he finished second in 2021 and 2024.

The Phillies, who began the day six games clear of the New York Mets in the NL East, will lean on Aaron Nola, Taijuan Walker and left-handers Cristopher Sánchez, Ranger Suárez and Jesús Luzardo to fill the void. Top prospect Andrew Painter, still finding form after Tommy John surgery, could also be called upon.

“It’s never good to lose a Zack Wheeler, your No 1 pitcher,” Dombrowski said. “You’re never going to replace an individual like that. But we have a good ballclub, and we’ll be looking for other people to step up and pick up the slack.”

Despite the setback, Thomson said he had not noticed a deflated mood in the clubhouse. “They’re baseball players,” he said. “They just kind of move on. We’ve got a game today. They’re not going to cancel it.”