ST LOUIS - Rickie Fowler, a top-five finisher twice in every major without a win to show for it, fired a five-under par 65 Thursday to grab an early two-stroke clubhouse lead at the 100th PGA Championship.

Ninth-ranked Fowler, who began on the back nine at Bellerive Country Club, drained a 31-foot birdie putt at the par-4 seventh hole and at the par-5 eighth reached a greenside bunker in two then blasted to eight feet and made the birdie putt to reach five-under. England's Ian Poulter birdied three of his first six holes and shared second, joining Americans Austin Cook and Pat Perez in the locker room on 67. "I got off to a flying start," Poulter said. "You definitely want to post a number on the fresh greens. They kept them a little slower than they wanted. It was a good day."

In the feature early pairing, defending champion Justin Thomas was on two-under with Rory McIlroy at level par and Tiger Woods at one-over through 16 holes. Considered a solid contender to win a major in his 20s when he turned pro at age 20 in 2009, Fowler has one final chance to lift a major trophy before turning 30 in December.

Fowler, who matched his best major showing with a runner-up effort at this year's Masters, had four top-five major finishes without a win in 2014, sharing second at the US and British Opens. He became the first player to top-5 in all four majors without a win. Fowler, who found 11 of 14 fairways and 16 of 18 greens in regulation, sank a five-foot birdie putt at 14 but at the par-3 16th found a bunker and made bogey. He bounced back with a 12-foot birdie putt at the par-5 17th, a 14-footer at the first and six-footer to birdie the third.

The superstar trio with Woods began off the 10th tee with thousands of spectators lining the fairway, standing 10 deep in spots just to glimpse the master shotmakers. Instead, Woods endured an early horror show, McIlroy was grinding and only Thomas was showing major champion form. Second-ranked Thomas, coming off a WGC victory Sunday, sank birdie putts from five feet at 11 and seven feet at 12, rescued par from a bunker at the par-3 13th and added another birdie at 15 before a bogey at the fourth dropped him back. Thomas, 25, could become the first player since McIlroy in 2014 to make the PGA his second win in back-to-back weeks and join Woods as the only men since 1937 to win consecutive PGAs.

Woods, a 14-time major champion in a comeback season after spinal fusion surgery, struggled from the start, finding right rough off the 10th tee and making a nervy five-foot bogey putt. The 42-year-old former world number one found water with his second shot on the way to a double-bogey six at 11 but dropped his approach to two feet and birdied the 12th. He was undone again at the par-3 16th, needing two chips to escape the rough and tapping in for bogey.

Woods battled back, however, sinking consecutive birdie putts from four feet at 18 and nine feet at the first.

Woods briefly led in the final round of last month's British Open, but he hasn't won a major since the 2008 US Open or any title since 2013. Four-time major champion McIlroy, whose last major triumph came in 2014, found a bunker at 10 and made bogey, then sank birdie putts from eight feet at 11 and 12 feet at the par-3 13th only to close his first nine with a bogey to stand on level par, then opened his second nine with seven pars.

Many players teed off with a heavy heart after Wednesday's death of Australian Jarrod Lyle, a former tour player who lost his battle with leukemia at age 36. Lyle, whose best US PGA Tour finish was a share of fourth in 2012 at Riviera, played 121 PGA events from 2006-2016. He was diagnosed with leukemia as a youth and twice thought he had beaten cancer only to have it return last year.

British Open champion Francesco Molinari was set for an afternoon start over the 7,316-yard, par-70 layout alongside this year's other two major winners -- Americans Patrick Reed from the Masters and Brooks Koepka from the US Open.