Wheeler’s outlook on his return from TOS – and what to expect in 2026

Wheeler’s outlook on his return from TOS – and what to expect in 2026 originally appeared on NBC Sports Philadelphia

When people look back on the 2025 Phillies, the loss of Zack Wheeler will always stand out.

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On August 15, the club revealed that the 35-year-old had a blood clot in his right upper limb. He was placed on the injured list two days later and underwent a successful thrombolysis ablation procedure a day later. On August 23, his season was declared over.

It was a punch in the gut. Wheeler was in the midst of one of his best years in Philadelphia – 10-5 with a 2.71 ERA, an elite 195/33 strikeout-to-walk ratio and a 0.94 WHIP over 24 starts.

The accumulation of injuries

The first sign of trouble came on Aug. 2, when right shoulder soreness after a start against Detroit pushed back his next outing by two days.

Wheeler beat Texas on August 10, but the radar gun told the story. Paul Casella of MLB.com noted that each pitch type plunged more than a mile per hour, including a 2.5 mph drop on his sinker and a 2 mph dip on his four seamer.

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So when IL’s decision became official, it wasn’t shocking – but it was certainly damaging. The Phillies have gone 17 games above .500. They had passed the trade deadline. Their plan to deploy a true six-man rotation to relieve Aaron Nola was in the rearview mirror.

Other updates would also come. On September 23, Wheeler underwent surgery for vascular thoracic outlet syndrome.

The Phillies adapted – Cristopher Sánchez led MLB in WAR (8.0) and carried the staff down the stretch – however, Wheeler’s absence was felt throughout the club’s unsuccessful trip to the postseason.

Now, with spring training about three months away, the Phillies have several questions about the rotation. Can Sánchez handle ace responsibilities throughout a full season? Can Jesús Luzardo match the production of Ranger Suárez, who is expected to leave in free agency? Who becomes the fifth holder?

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But one question takes precedence over the others: what version of Zack Wheeler will the Phillies get?

Recent history of “TOS”

TOS has become a buzzword for pitchers – and a scary one. Notable starters Matt Harvey, Josh Beckett and Stephen Strasburg all had surgery. None returned to their pre-injury form and Strasburg never pitched again.

But not all terms of use are the same. Vascular TOS – of the Wheeler type – produced stronger results than the neuronic version that derailed Strasbourg’s career.

The clearest example is Merrill Kelly.

As detailed in Report by Charlotte Varnes for The AthleticKelly suffered a vascular TOS after the 2020 season and returned without delay, making 27 starts in 2021 and posting a 3.66 ERA over 135 starts over the next five seasons.

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Expectations and timeline

This story matters as the Phillies try to evaluate Wheeler’s prospects.

Since joining Philadelphia in 2020, Wheeler has a 2.91 ERA. If he returns with an ERA between 3.30 and 3.50, history says that would already be considered a successful return. There is optimism internally because the Phillies no longer need Wheeler to single-handedly man the rotation — Sánchez’s emergence has changed that dynamic.

“It helps, but I would prefer to have Zack Wheeler back and Cristopher Sánchez,” Dombrowski said in his end-of-season press release. “I’ve dealt with thoracic outlet syndrome before – there are differences in TOS – and I feel much more optimistic.”

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As for the schedule, there have been no updates since mid-October. According to Dombrowski, “The time frame remains six to eight months to return to a championship game – so that brings you to the end of May. I don’t think it will affect us much because we are waiting for his return on that schedule.”

That makes an opening day return unlikely. But Wheeler will be deep into his throwing progression throughout spring training.

It’s difficult to attach firm expectations to a pitcher who turns 36 on May 30, especially after major surgery. But if there’s been one constant during his tenure in Philadelphia, it’s that Zack Wheeler has earned the benefit of the doubt.

The Phillies don’t need Wheeler to recreate his 2021 or 2024 Cy Young runner-up seasons to return in October. And with recent reports indicating they won’t be looking for a starter this winter, the plan is clear.

If he returns healthy – and somewhere close to his pre-injury form – they will have the stabilizer they lacked during their run to the 2025 playoffs.