Alex Reyes has a partial tear of the ulnar collateral ligament in his elbow and will get a second opinion, but season-ending Tommy John surgery is likely for the St. Louis Cardinals pitcher, according to a source.

Reyes was scheduled to undergo an MRI on Tuesday afternoon.

John Mozeliak said the Cardinals will wait until Wednesday morning before making any announcement about the next step.

"I'm concerned about Reyes. Any time you send someone to get an MRI, it's concerning. I'm not going to speculate what the MRI is going to say. We'll save that for tomorrow," Mozeliak said.

Reyes, 22, made his major league debut Aug. 9 and was 4-1 with a 1.57 ERA in five starts and seven relief appearances.