The Reds transferred Williamson (elbow) to the 60-day injured list Tuesday.

Williamson said Wednesday that he has a full UCL tear in his left elbow and will require Tommy John surgery, Mark Sheldon of MLB.com reports.

The Reds placed Williamson on the 15-day injured list Wednesday with a left elbow strain.

Williamson was removed from his start Tuesday against Atlanta with an apparent injury, Gordon Wittenmyer of The Cincinnati Enquirer reports.

Williamson did not factor into the decision in Sunday's win over Milwaukee, allowing two earned runs on four hits and zero walks while striking out five in 3.1 innings.

The Reds reinstated Williamson (shoulder) from the 60-day injured list ahead of his scheduled start Sunday versus the Brewers.

Williamson (shoulder) struck out four and gave up one hit and one walk over 2.2 scoreless innings in his rehab start Tuesday for Triple-A Louisville.

Williamson (shoulder) is scheduled to start for Triple-A Louisville on Tuesday, C. Trent Rosecrans of The Athletic reports.

Williamson (shoulder) is expected to begin a rehab assignment next week, Charlie Goldsmith of the Cincinnati Enquirer reports.

Williamson (shoulder) will throw a bullpen session July 23, Charlie Goldsmith of The Cincinnati Enquirer reports.