Reyes underwent an MRI at the Hospital for Special Surgery in Manhattan after aggravating a right calf injury that had been bothering him for more than a week.
The MRI showed that Reyes has tendinitis behind his right calf and he is officially listed as day-to-day. At this point, he has not been placed on the DL.
Reyes was back in the lineup Wednesday night after missing a few days with the injury, but left in the third inning after re-injuring the calf while running up the line on a ground ball.
He left the game and was replaced at shortstop by Ramon Martinez.
"He felt some pain and discomfort," Mets manager Jerry Manuel said. "It was obvious that he was struggling. But how much damage he had done or was it just a shock of pain, we don't know."
"It's the same problem that I've had the last couple of days," Reyes said. "It still bothers me. It's still painful."
The Mets are off Thursday night.