Mets’ Roster Hopeful Needs Dreaded Thoracic Outlet Syndrome Surgery

Mets reliever Robert Stock was recommended for thoracic outlet syndrome surgery, likely sidelining him most of 2026.

Mar 15, 2023; Miami, Florida, USA; Israel starting pitcher Robert Stock (89) delivers a pitch during the third inning against Venezuela at LoanDepot Park. Mandatory Credit: Sam Navarro-Imagn Images | Sam Navarro-Imagn Images

After initially reporting shoulder discomfort earlier this week, New York Mets roster hopeful Robert Stock now faces a lengthy absence.

On Sunday, Stock told reporters (including Jon Heyman of the New York Post) that he was recommended for surgery to correct thoracic outlet syndrome. The right-hander has a rare form called arterial TOS, which can cause a feeling of coldness in the hand or even finger gangrene. He said he could possibly return by the end of the year, though the typical recovery period for a pitcher is about nine to 10 months.

Stock furthermore was told he has the “bad” kind of TOS, whereby the artery is compressed. Stock reported shoulder discomfort following three dominant shutout innings for team Israel versus the Marlins https://t.co/1eKFjnVtxU

— Jon Heyman (@JonHeyman) March 8, 2026

Stock, 36, signed a minor league contract with the Mets this offseason after spending 2025 in the Boston Red Sox organization. He was in camp as a non-roster invitee before joining Team Israel ahead of the World Baseball Classic.

A second-round pick in 2009, Stock owns a 4.90 ERA over 75.1 career MLB innings. He did not appear in the majors from 2022-24, instead bouncing between the KBO, the minor leagues and independent leagues in both the United States and Mexico. In 2025, he allowed three earned runs over 2.2 innings for the Red Sox and had a 3.92 ERA over 85 innings with Triple-A Worcester.

Stock impressed in a limited sample size this spring. He tossed three scoreless innings for the Mets on Feb. 26, allowing one hit with no walks and six strikeouts. During Team Israel’s exhibition game against the Miami Marlins on Tuesday, he struck out three and generated eight whiffs over another three scoreless frames. That outing ended with him reporting shoulder discomfort.

Robert Stock for Team Israel against the Marlins:

3 IP, 2 H, 0 R, 1 BB, 3 K, 8 whiffs

Fastball was up to 97.9 mph.

Stock pitched three scoreless innings with six strikeouts in his first spring outing for the Mets last week.

— Mike Mayer (@mikemayer22) March 3, 2026

Arterial TOS is far less common than other forms baseball fans have become familiar with in recent years, leaving its impact on players relatively unknown. Former Washington Nationals ace Stephen Strasburg notably had his career derailed by neurogenic TOS, which is a compression of the nerves, while current Philadelphia Phillies ace Zack Wheeler was sidelined late last year by venous TOS.

There are examples of pitchers who have returned from TOS at a high level, including Merrill Kelly and Alex Cobb. However, some never regain their command, velocity and/or effectiveness.

Whether or not Stock returns to the mound this year, the Mets have plenty of bullpen depth available to step up in his absence. Among the relievers on the roster bubble are Bryan Hudson, Craig Kimbrel, Huascar Brazobán, Joey Gerber, Justin Hagenman, Carl Edwards Jr. and Nick Burdi — some of whom could begin the season with Triple-A Syracuse.

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