"The initial diagnosis shows that Rory has strained a tendon in his right wrist," said a statement from ISM, McIlroy's management company. "He will obviously rest it tonight, and he will see how it feels in the morning on the range."
McIlroy shot an even-par 70 on Thursday after hurting the wrist when he hit a root with his second shot at the third hole.
The U.S. Open champion iced the wrist, then got a physical therapist to work on the injured wrist and arm on the fifth green. When the trainer told him he couldn't do further damage, McIlroy continued on and played pretty well.
"To be honest, considering I finished with one hand, I hit some good shots," said McIlroy. "It was always there in my mind. So to shoot even par, it was a good effort."
McIlroy, who had his wrist and forearm taped during the round, is seven shots behind leader Steve Sticker after the opening round at Atlanta Athletic Club.