Defending champion Rory McIlroy today blamed agonising toothache after pulling out of the Honda Classic midway through a second round that was becoming embarrassing.
The Northern Irishman, ranked number one in the world, began on the back nine at the Palm Beach Gardens course and played his opening eight holes of the round in seven over par.
He then found the water at the 18th - his ninth hole - and immediately quit the tournament.
McIlroy had a level-par 70 yesterday, but was set to miss the cut after his flurry of dropped shots before deciding enough was enough. He had double-bogeyed the 11th, taken a seven at the par-four 16th, and also given shots away at the 13th and 17th holes.
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."
He was playing in a group with Open champion Ernie Els and American Mark Wilson.
In a statement on pgatour.com, McIlroy added: "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."
The 23-year-old has struggled to rediscover the form that has elevated him to the top of the world rankings so far in 2013, highlighted by his first-round exit at the Accenture Match Play Championship to Ireland's Shane Lowry last week.
He signed a lucrative sponsorship deal with Nike last month and his performances with the manufacturer's clubs have fallen below expectations.
McIlroy also missed the cut at the Abu Dhabi HSBC Championship by four shots last month.
The link between McIlroy's slump in form and his new clubs has already been speculated on, but he dismissed concerns about ball control only yesterday.
The PGA Tour today reported it was the first time McIlroy has withdrawn during a tournament.
American Michael Thompson led on eight under par in the closing stages of his second round, two shots ahead of Australian Geoff Ogilvy and England's Lee Westwood who were his nearest challengers.
Thompson was in the first group off from the first tee this morning and was playing the 18th.
McIlroy's compatriot Graeme McDowell was tied for fourth place on five under, with many in the field still to begin their second rounds.