Rory McIlroy - Defending champion and world No. 1 - withdrew before finishing his first nine holes in Friday's second round of The Honda Classic.
No immediate word was given for his withdrawal, though he didn't appear to be injured or sick.
After hitting his approach shot into the water on the 18th -- his ninth hole of the day -- McIlroy walked off the course and quickly left the course with his coach and caddie.
McIlroy, who started on No. 10, struggled from the start. He nearly hit his approach on the 11th hole into the water before chipping through the green and making double bogey.
Two holes later, he made another bogey after driving it well right and being forced to lay up. He missed a 6-footer to save par.
Things went from bad to worse on the par-4 16th. McIlroy hit his tee shot into the water, took a drop, then hit another into the water before carding a 7.
On the par-3 17th, McIlroy three-putted from just over 40 feet to fall to 7 over through his first eight holes.
His troubles began on his second hole, No. 11, where he nearly hit his approach into the water before chipping through the green and eventually making double bogey.
Two holes later, McIlroy drove it into the right rough and had to lay up. His putt to save par from 6 feet slid past the hole and he made another bogey.
Then things went from bad to worse.McIlroy drove it in the water on the par-4 16th, took a drop, then hit it in the water again. He made 7.
At the par-3 17th, McIlroy found the green with his tee shot, but three-putted from 42 feet after running his first putt 10 feet past the hole.
This is the first time in McIlroy's career that he has withdrawn from a tournament.
Rory released a statement through the PGA Tour, citing wisdom tooth pain for his exit.
He said: "I sincerely apologise to the Honda Classic and PGA Tour for my sudden withdrawal.
"I have been suffering with a sore wisdom tooth, which is due to come out in the near future. It began bothering me again last night, so I relieved it with [painkiller] Advil.
"It was very painful again this morning, and I was simply unable to concentrate. It was really bothering me and had begun to affect my playing partners."
His statement continued: "I came here with every intention of defending my Honda Classic title. Even though my results haven't revealed it, I really felt like I was rounding a corner.
"This is one of my favourite tournaments of the year and I regret having to make the decision to withdraw, but it was one I had to make."
Speaking to the PGA Tour website, McIlroy said: "It's hard to commit to the shot that you need to play every time. If you know that you should play a fade and you're not comfortable with it, it's hard to do."
Asked if he was close to fixing his swing, he added: "Definitely. I felt like I hit the ball okay, not as good as I can, but it's getting there."
He was playing in a group with Open champion Ernie Els and American Mark Wilson.
