World No. 1 and defending champion Rory McIlroy withdrew from the US PGA Honda Classic during his second round on Friday, saying he was struggling due to pain from a sore wisdom tooth.
McIlroy struggled through the back nine on Friday, his opening nine holes of the round, and hit his approach at the 18th into water. He then walked off the course and quickly departed the grounds with his coach and caddie.
"I sincerely apoloize to The Honda Classic and PGA Tour for my sudden withdrawal," McIlroy said. "I have been suffering with a sore wisdom tooth, which is due to come out in the near future."
It was the first time in his career that McIlroy withdrew from a tournament and it comes as the 23-year-old from Northern Ireland struggles to find his form after switching to Nike equipment for this season.
McIlroy is a 6-1 co-favorite with 14-time major champion Tiger Woods in next month's Masters, but the tooth issue could dim his bid to add to a major haul that includes the 2011 US Open and 2012 PGA Championship.
"It began bothering me again last night, so I relieved it with Advil," said McIlroy. "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."
Especially gutting for McIlroy was the fact the pain flared as he was trying to defend the title he won a year ago to put himself atop the world rankings for the first time in his career.
"I came here with every intention of defending my Honda Classic title," said McIlroy. "Even though my results haven't revealed it, I really felt like I was rounding a corner. This is one of my favorite tournaments of the year and I regret having to make the decision to withdraw, but it was one I had to make."
McIlroy, who missed the cut in his first 2013 start at Abu Dhabi and lost in the first round of the WGC Match Play Championship last week, opened with a par-70 on Thursday but admitted he was still working on his timing and adjusting to his new clubs.
"It's hard to commit to the shot that you need to play every time," McIlroy said Thursday. "I felt like I hit the ball OK, not as good as I can, but it's getting there."