PHILADELPHIA — As Zack Wheeler consulted specialists for a second and third opinion this week, the Phillies feared the worst. They operated with the assumption that Wheeler would not throw another pitch for them in 2025, a debilitating blow to a club carrying a franchise-record payroll and the highest of expectations. They had hoped for a miracle — that the blood clot removed from Wheeler’s right shoulder area was not the sign of a deeper problem.

But there was a consensus among the specialists. Wheeler was diagnosed with venous thoracic outlet syndrome and must undergo surgery to remove a rib. The Phillies estimate he’ll need six to eight months of recovery, which means his absence could seep into the 2026 season.

Wheeler, who turns 36 next May, faces a major hurdle to continuing his career at an elite level.

“We figure that he’ll come back in the six-to-eight month time period and come back and be the Zack Wheeler of old,” Phillies president of baseball operations Dave Dombrowski said Saturday. “That’s what we’ve been told. Unless something unanticipated happened, he’ll be able to come back and pitch like he has before this.”

This procedure is considered far riskier than, say, elbow reconstruction through Tommy John surgery. It has ended careers or transformed pitchers into far diminished versions. But Wheeler’s version of thoracic outlet syndrome (TOS) is not the most common among pitchers, the one that can damage nerves.

Wheeler could begin throwing again eight weeks after the surgery, Phillies head athletic trainer Paul Buhcheit said. Wheeler slipped into Citizens Bank Park on Friday afternoon to see the medical staff. After the game, word began to spread through Wheeler’s teammates about his prognosis. Buccheit, who has grown close to Wheeler during their fastidious between-starts routine, was one of the few to actually see Wheeler.

“He’s doing well,” Buchheit said. “He’s doing fine.”

Wheeler was resting at home after a procedure to remove the blood clot, then he traveled to see what Buchheit referred to as “the leaders in the industry on this.” The surgery, a thoracic outlet decompression, has yet to be scheduled.

The sport is littered with TOS survivors and horror stories. It’s an ailment that ended Stephen Strasburg’s career, but Strasburg suffered from the nerve-related TOS. The closest comparison to Wheeler might be Merrill Kelly, who developed a blood clot in his shoulder late in the 2020 season. He was diagnosed with venous TOS and underwent surgery to remove a rib on Sept. 9, 2020, about a month before his 32nd birthday. He returned to start the second game of the 2021 season for the Arizona Diamondbacks and has made 129 starts since.

Merrill Kelly has made 129 starts since undergoing a similar surgical procedure that awaits Zack Wheeler. (Jamie Squire / Getty Images)

“The blood clot was not fun,” Kelly told The Washington Post in 2023. “They are life-threatening. But for pitchers, TOS surgery to address a blood clot is much more straightforward than nerve issues. The diagnosis is more straightforward. The recovery is more straightforward. I was lucky in that way.”

Buchheit reiterated the club’s stance that Wheeler’s TOS diagnosis was not related to the general shoulder pain he pitched through for numerous weeks.

“It was more of an acute issue,” Buchheit said. “That also is in his favor, that he wasn’t dealing with this for a long time prior to undergoing the procedure.”

The nerve-related TOS often presents through numbness or tingling in a pitcher’s fingers or hand. Often, pitchers push through early onset TOS symptoms because they’re not serious enough. But they can lead to bigger problems through changing postures or mechanics to overcompensate.

Wheeler’s release point had been dipping for weeks; the Phillies worked before his final start to correct things. His release point was higher during his Aug. 15 start than it had been in six weeks. They were all encouraged by the five-inning outing against the Washington Nationals.

Then, not long after, Wheeler needed to see the Nationals’ doctors.

“If you have symptoms from a neurological perspective, they may be present for a long time,” Buchheit said. “It takes a while to kind of evaluate and treat through. And a lot of times, you don’t go to a surgical option right away. With Zack, it was an acute onset. So he doesn’t have that long, protracted time period where he’s been battling things. The surgeons say that he’s going to have a really good prognosis with this.”

No one will know until Wheeler can start throwing a baseball again. Alex Cobb had a blood clot during his rookie season in 2011, underwent the TOS surgery and has been an effective big-league starter for 12 seasons since. Carter Capps, a hard-throwing reliever who had previous elbow issues, needed the TOS surgery after developing a blood clot during the 2017 season. He never pitched again in the majors.

Every case is different.

Wheeler was the sport’s highest-paid pitcher this season; he has two seasons remaining on a three-year, $126 million deal. He has fully intended to stop pitching once that contract ends. For most of this season, he pitched at the highest level. He overcame injuries earlier in his career and morphed into one of the surest things in baseball.

Now, he faces an enormous challenge. So do the Phillies, who must push forward in 2025 without their best pitcher.

(Photo: Sean M. Haffey / Getty Images)