Zack Wheeler's successful return to the Philadelphia Phillies' starting rotation is one of the most important early-season priorities for the club. For the most part, his recovery from thoracic outlet syndrome has gone well, which is good news for a club with World Series aspirations.
Slated for a return in April, when Wheeler is activated, it will give Philadelphia options. The club could decide to go the six-man rotation route, at least for a little while. That might be a wise plan to keep Wheeler healthy, as well as take some pressure off the existing crop of starters who will be counted on to make a deep playoff run.
But as Wheeler works his way back at Lehigh Valley, he isn't free of concern. The ace right-hander still hasn't seen his velocity return, and the disparity from where he was at and what he's pushing now should bring about some worry.
Zack Wheeler continues to have big velo concerns pic.twitter.com/dvrYNxdhI3
— Mike Kurland (@Mike_Kurland) April 4, 2026
Typically sitting around 96 miles per hour on his fastball for his career, Wheeler has taken over a three miles per hour hit in his latest start, sitting at 92.7 miles per hour and maxing out at 93.9 on the gun. Velocity isn't the end-all be-all, but we're also not talking about a small decrease here, and it could have some big implications.
Understanding Zack Wheeler's diagnosis and whether Phillies fans should fear this velocity drop
A better understanding of Wheeler's condition is required to determine whether or not we should be concerned. While most reports simply state that he underwent surgery to deal with thoracic outlet syndrome, there are actually three different variations of the condition.
Venous thoracic outlet syndrome is what Wheeler was treated for, and essentially means that pressure was being put on one of the veins passing through his shoulder to his neck. To correct this, he had a rib removed to alleviate the pressure and clotting in his shoulder. This is different than neurogenic thoracic outlet syndrome, where the cause is related to the compression of the nerves rather than the veins.
Neurogenic thoracic outlet syndrome is the most common variant we see among MLB pitchers, and it is the ailment that ultimately derailed Stephen Strasburg's career.
Across all types of thoracic outlet syndrome, the condition is relatively rare. According to a study from the Orthopedic Journal of Sports Medicine, 26 pitchers underwent the rib resection procedure that Wheeler needed from 2001 to 2019. Of those 26 hurlers, 81% of them returned successfully, and the study didn't find any trend of significant drop-off in performance.
A similar study from 2001 to 2017 identified 27 pitchers who underwent treatment for thoracic outlet syndrome, though only seven had the venous condition. In this instance, 74% were able to return, and there was no significant drop-off in performance.
That's mostly encouraging, but there are a couple of things to consider. First, the samples are small to begin with and minuscule when it comes to the exact condition that Wheeler was suffering from. Secondly, while the first study doesn't speak to age, in the second, the median age was 28.6 years old. Wheeler turns 36 on May 30 and already has a lot of miles on that right arm.
With all that said, it's not time to panic yet, but it's important to remember that this was a serious injury, and we're in relatively uncharted territory. There's the potential that his velocity will tick back up as he continues his rehab, and we'll have nothing to worry about. But, there's also a chance that this is the new reality for Wheeler, and he'll have to reinvent his game to work with less power. For now, it's a situation to monitor, and the Phillies should already be drawing up plans to try to manage his workload to give him a boost once he returns.