NEW YORK -- Mets right-hander Noah Syndergaard encountered another hurdle in his recovery from Tommy John surgery Sunday when he was scratched from a rehab start because he tested positive for COVID-19, according to multiple reports.

New York manager Luis Rojas said Sunday that Syndergaard had a "non-baseball-related injury." He did confirm that Syndergaard has been vaccinated.

Syndergaard -- who turned 29 on Sunday -- tweeted, "This birthday is so sick."

This birthday is so sick. pic.twitter.com/EqGqwWUF1T

— Noah Syndergaard (@Noahsyndergaard) August 29, 2021

Syndergaard, who hasn't pitched in the majors since Sept. 29, 2019, had the surgery just after the pandemic shutdown in March 2020. He began a rehab assignment this spring but left his second start with Low-A St. Lucie on May 26 with right elbow inflammation.

Syndergaard, who is scheduled to reach free agency after the season, didn't pitch again until Thursday's rehab outing, when he gave up one run in one inning. Afterward, he said he wasn't throwing his slider or curveball because doctors believed the off-speed pitches bothered his elbow.

With no time to build up Syndergaard to a typical starter's workload, the Mets are hoping he could rejoin the team as a reliever. He had been expected to throw at least an inning Sunday for Single-A Brooklyn.

The news of Syndergaard's positive test result was first reported by Newsday.

The Associated Press contributed to this report.