By Simon Evans
PALM BEACH GARDENS, Florida, March 1 (Reuters) - Young American Luke Guthrie shot a sparkling seven-under-par 63 to grab the early clubhouse lead at the Honda Classic on Friday after world number one Rory McIlroy withdrew citing a toothache.
The 23-year-old Guthrie, yet to win on the PGA Tour, was flawless as he carded seven birdies at PGA National to gain a one stroke lead over compatriot Michael Thompson (65).
Britain's Lee Westwood and Australian Geoff Ogilvy put themselves in contention for the with rounds of 68 and 66, respectively, to lay three strokes back of Guthrie.
Westwood said he was taking a cautious approach to the challenging course, which on Friday remained very soft with frequent mud on balls.
"It's a tough setup and it's one of the more demanding tests of the year," said the Englishman. "There's trouble out there; if you get a good game plan, then you can get around it. Once you start getting a bit cute and chasing, it can bite you."
Tiger Woods, coming off an opening-round 70 and playing in the later groups, was even-par through seven holes after following birdies at the fourth and fifth holes with bogeys at the par-four sixth and par-three seventh.
But the attention was all on world number one McIlroy, who had a nightmare start to his second round, dropping seven shots from his opening eight holes with a triple-bogey, a double-bogey and two bogeys.
The Northern Irishman, who before the tournament conceded he was adjusting to his Nike clubs after switching from Titleist in January and had also complained of swing troubles, released a statement saying he had severe wisdom tooth pain.
"It began bothering me again last night," 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."
McIlroy's withdrawal will further increase scrutiny on his play after his elimination in the opening round of the WGC-Accenture World Match Play Championship last week in Arizona.
The Northern Irishman also missed the cut at the Abu Dhabi Championship in January. (Editing by Frank Pingue)