PALM BEACH GARDENS, Florida, March 1, 2013 (AFP) - Guthrie fired a bogey-free 63, seven-under par, to grab a one-stroke lead over countryman Michael Thompson on nine-under 131 after 36 holes of the $6 million tournament on a day when McIlroy's walkout stole the major attention.
McIlroy, who missed the cut in Abu Dhabi and was ousted in the first round last week at the World Golf Championships Match Play event in his only prior starts this year, continued to struggle with his new Nike equipment.
After starting on the back nine, McIlroy had a double bogey, triple bogey and two bogeys before finding the water off the tee at the 18th and leaving behind playing partners Ernie Els and Mark Wilson as he walked off the course.
"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.
"I was simply unable to concentrate. It was really bothering me and had begun to affect my playing partners."
And as McIlroy's bid to repeat as champion ended in tatters, World No. 2 Tiger Woods fared little better. The 14-time major champion fired his second 70 in a row to make the cut only on the number.
Woods birdied the fourth and par-3 fifth holes but made bogeys on the next two holes. He closed the front nine with a birdie, stumbled to a double bogey at the par-4 13th but birdied 14 and parred in to reach the weekend.
"I've got to get something going," Woods said. "There are 70 guys within nine shots of the lead. It's pretty well bunched. I've got to give myself a good chance to win it."
Leader Guthrie, by contrast, is a tour rookie whose best finish in his eight prior PGA events was a share of fifth at last year's John Deere Classic. But he pulled off the round of the day to move atop the leaderboard.
Guthrie began on the back nine and capped a run of three birdies in four holes with a 2 on the par-3 15th. Birdies at the first and third solidified his run at the lead and he took the top spot with birdies at the sixth and seventh.
Thompson was second with Canada's Graham DeLaet and American Boo Weekley sharing third on 133, one stroke ahead of a group of six that included England's Lee Westwood and Justin Rose and Australian Geoff Ogilvy.
Leading scores on Friday after the second round of the $6 million US PGA Honda Classic (USA unless noted, par-70)
131 - Luke Guthrie 68-63
132 - Michael Thompson 67-65
133 - Boo Weekley 66-67, Graham DeLaet (CAN) 65-68
134 - Lee Westwood (ENG) 66-68, Geoff Ogilvy (AUS) 68-66, Doug LaBelle 66-68, Charles Howell 67-67, Sean O'Hair 66-68, Justin Rose (ENG) 68-66
135 - Graeme McDowell (NIR) 67-68, Robert Streb 65-70, Brian Stuard 66-69, Nicholas Thompson 69-66, Lucas Glover 69-66, Tom Gillis 67-68, Billy Horschel 66-69
136 - Daniel Summerhays 69-67, Chris Kirk 68-68, Keegan Bradley 68-68, Rickie Fowler 65-71, Jeff Klauk 67-69, Branden Grace (RSA) 65-71
137 - James Driscoll 69-68, Ross Fisher (ENG) 71-66, Cameron Percy (AUS) 71-66, Dustin Johnson 66-71, Martin Kaymer (GER) 71-66, Erik Compton 69-68
WD - Rory McIlroy (NIR) 70, Brian Davis (ENG) 78