Middleton (forearm) will undergo an MRI on Friday and could require season-ending surgery on his pitching arm, John Denton of MLB.com reports.

EDGE Analysis

Middleton was evaluated by team doctors Tuesday, and the organization seems to have concern that he's dealing with a significant arm injury. If he does ultimately require surgery, his season would end before it began, as Middleton has been shelved since spring training with what's been termed a right forearm strain. The reliever signed a one-year, $6 million contract with the Cardinals back in February.