HILTON HEAD ISLAND, S.C. (AP) -- Colt Knost believes he's finally ready to succeed on the PGA Tour, no matter how much work he's got ahead at the RBC Heritage.
Knost shot a 6-under 66 on Friday to take a two-stroke lead over Carl Pettersson after the second round. Knost, tied for the first-round lead with Chad Campbell and Vaughn Taylor after a 67, had three birdies in a four-hole stretch midway through the round and finished at 9-under 133.
Pettersson had a 65, his best ever showing in 32 career rounds at Harbour Town Golf Links. Two-time RBC Heritage winner Boo Weekley (66) and Harris English (68) were another shot off the lead at 6 under in a week when Masters champion Bubba Watson and most of the world's best took a break following the year's first major.
World No. 1 Luke Donald, though, was among the few stars at Harbour Town. He needs a top-eight finish to retain the top spot over idle No. 2, Rory McIlroy, and bounced back from an opening 75 with a 69 to slide inside the cut line.
Campbell (70) and Robert Garrigus (66) were four shots behind. Defending champion Brandt Snedeker had five consecutive birdies on the way to a 67 and was tied with Michael Bradley (64), Kevin Na (68), Bob Estes (67) and Fredrik Jacobson (67) at 4 under.
The 26-year-old Knost was one of the fastest risers in golf a few years ago, winning the U.S. Amateur, the U.S. Public Links championship and helping the American team win the Walker Cup in 2007. He won twice on the Nationwide Tour in 2008, his first season as a pro, and easily qualified for the big tour. Even more winning was ahead, right?
"I felt like I was ready for this level out here," Knost said. "And apparently, I wasn't."
Knost missed the cut in 13 of 24 tour events that year and earned just $180,734 to lose his card after 2009. He regained playing privileges after another season on the Nationwide Tour and yet again struggled at the higher level, missing cuts in 15 of 26 events.
Knost held on to his tour card in gut-wrenching experience at Q-school - he was in tears when he thought a double bogey on the 108th and final hole cost him the PGA Tour - and has since tried to rediscover the work habits and confidence that made him one of the decade's best amateurs.
"I don't know if I just didn't continue with the same work ethic or not or I didn't have the belief, but it was a struggle for a few years out here," Knost said. "But now I feel like I'm starting to get my game back where I like it."
Knost certainly liked his second-round performance.
Knost's round got going with a stretch of three birdies in four holes to give him the lead at 8 under. He made his final birdie on the par-5 fifth and finished off the bogey-free round that stoked his confidence.
"I felt so comfortable out there being around the lead, even though it's only Friday," he said. "I think I'm also going to feel great this weekend."
Pettersson won't feel too bad, either. He posted his career-low score in 32 rounds over Harbour Town highlighted by a run of three straight birdies on the second, third and fourth holes.
"My game is good," said Pettersson, whose last of four tour wins came at the 2010 Canadian Open. "In golf, you still have two days, which is a long way to go."
Weekley's only two PGA Tour wins came at the RBC Heritage in 2007 and 2008 and turned him into golf's true life "Happy Gilmore," complete with a "pony ride" with his driver off the tee during Ryder Cup matches in 2008 to the delight of U.S. fans. Things weren't much fun for Weekley after that as his performance dropped off dramatically. He missed 10 cuts in 2010 and 11 the next season as he struggled to overcome a torn labrum and a cyst in his left shoulder from 2009 that was "like a big pocket of junk," Weekley said.
He's got a new instructor in Scott Hamilton and a new caddie in John Connelly who "reads the greens good where I struggle a lot," Weekley said.
Now, healthy, Weekley wants to show he's the golfer who earned a spot on the Ryder Cup team with his play and not just for clowning around. He posted six birides and one bogey to shoot himself into contention. "This golf course just suits me," he said.
Weekley's never all just about golf. He explained how his stomach gave him some "reflux" before the round he thought "I was going to do a little yodeling out there."
Weekley kept his gastrointestinal issues mostly to himself on the course as he posted his 14th career round in the 60s out of 22 played here.
Donald came out firing in the second round with birdies on the second, sixth and seventh holes. He needed par saves, though, on Harbour Town's three finishing holes, including a testy four-footer on No. 18, to reach the weekend.
He said staying No. 1 is a motivator. "But the goal obviously is to get in contention and win," Donald said. "You can't control the other stuff."
Not everyone was as fortunate as Donald.
Those missing the cut here included No. 18 in the world and last year's FedEx Cup champion Bill Haas and a pair of three-time major champions in Ernie Els and Padraig Harrington. Els, who missed the Masters last week after 18 straight appearances, shot an 8-over 43 on his final nine holes, including a triple-bogey 7 on the 18th that kept him from playing the weekend.
Divots: Jim Furyk, the 2010 champion, was a stroke off the lead Thursday, but ballooned to a 75 on Friday to fall 10 shots off the pace ... Camilo Villegas and Alex Cejka withdrew because of injury. ... Bradley shot the tournament's low round of 64 in the second round. ... Bob Estes had the second hole-in-one of the tournament, hitting a 6-iron into the cup on the 183-yard fourth hole. Billy Mayfair had an ace on the seventh hole Thursday. It's the fourth time in the past five tournaments there have been two holes-in-one during competition. ... John Daly following his first-round 70 with a 74, good enough to make his sixth straight cut at Harbour Town. ... The Boeing 787 Dreamliner aircraft did a low flyover of Harbour Town's 18th hole. Boeing is the tournament's presenting sponsor.