Gray was removed from Tuesday's loss to the Brewers due to tightness in his right groin, Bobby Nightengale of The Cincinnati Enquirer reports.
The right-hander struck out five over three scoreless frames before he was pulled after experiencing tightness while warming up for the fourth inning. Gray will undergo an MRI on Wednesday to determine the severity of the injury, leaving his status for his next turn through the rotation up in the air.