The spasms were not thought to be serious enough to keep him out of The Players Championship next week, where McIlroy will set out as the defending champion.

Even so, it was his first significant back issue since the Tour Championship in 2023, when he played with some discomfort. A month later, though, he went 4-1 while leading Europe to another Ryder Cup victory.

McIlroy is approaching a big stretch in golf that culminates with the first major of the year, the Masters, on April 9-12, with the Northern Irishman starting there as the defending champion. He won last year to become only the sixth player with the career Grand Slam.

McIlroy withdrew about 30 minutes before his tee time on Saturday. One of his managers said he experienced muscle spasms that didn't go away as he tried to warm up on the range during warm weather at Bay Hill.

It was only the third time McIlroy has been forced to withdraw from a tournament.

He left the Nedbank Golf Challenge in 2009 with a flu virus and food poisoning, and he withdrew from the Honda Classic in the middle of the second round in 2013, first citing a sore wisdom tooth and, a week later, apologising, saying his head was not in the right place.