American Jim Furyk leapfrogged Jason Dufner to snatch a one-shot lead after Saturday's penultimate round of the PGA Championship, as Rory McIlroy battled his way back into the tournament.
Furyk, who began the round two shots back of Dufner in a three-way tie for second, drained a 15-foot birdie putt on the par-four 17th en route to a two-under-par 68 that put him at nine-under 201 for the year's final major.
Dufner (71) scrambled a par on the 18th after sending his tee shot into the deep rough, but a brilliant approach to about 10 feet and a putt that caught the lip and dropped into the cup, left the second round leader alone in second.
Swede Henrik Stenson (69) was a further shot back while compatriot Jonas Blixt moved into fourth with a bogey-free 66.
Masters champion Adam Scott began the day level with Furyk and Matt Kuchar (76) but slipped into a tie for fifth place with Steve Stricker (70) after a two-over 72 that included a double-bogey six at the 16th.
Furyk offset two early bogeys with a pair of birdies on the front nine and then grabbed the outright lead with a birdie on the 10th.
He traded a birdie for a bogey over his next five holes before draining that long putt on 17 that put him in prime position to claim his first PGA Tour win since 2010 and his first major since the U.S. Open in 2003.
Dufner was cruising along with a string of pars and leading by three when his tee shot at the par-four fifth went into a creek.
After sending his third shot right of the green and chipping well past the hole, Dufner two-putted for a double-bogey six that cut his lead to one stroke.
The PGA Championship runner up in 2011, Dufner opened his back nine with a birdie before making pars the rest of the way, most notably at 18 when he looked headed for a sure bogey after an errant tee shot.
Only 11 of 75 players in action on Saturday managed to break par as sunny skies and blustery conditions combined to make Oak Hill's greens quicker and low scoring at a premium.
Scott got off to a quick start by draining a 20-foot birdie putt at the first to move one back of playing partner Dufner but bogeyed the next two holes to slip further behind.
The Australian then went on a string of 10 consecutive pars and birdied 14 to move back into the mix but his hard work was undone on the 16th.
Kuchar also got to within one shot of Dufner with a birdie putt at the opening hole after his approach from 186 yards landed about three feet from the pin.
But he had a double-bogey and three bogeys over his next eight holes to slide down the leaderboard.
The game's two leading players, Tiger Woods and Phil Mickelson, both tumbled out of contention, Woods battling to a 73 and Mickelson returning a 78.
Woods started the day 10 strokes off the pace and finished 13 behind and tied for 46th. He bogeyed two of his first three holes and managed just one birdie all day.
Mickelson, who captured his fifth major title at last month's British Open, fared even worse, ending the day 19 shots off the pace, in last place of the 62 players who made the cut.
McIlroy, who was five over for the tournament at one point on Friday and in danger of missing the cut, roared back into contention with a three-under 67 that included four birdies and a bogey.
The defending champion capped his round in brilliant fashion, taming Oak Hill's infamous tough closing stretch with birdies at 17 and 18, including a chip-in from behind the green at the last.
"The way the conditions are with the swirling wind, it's tricky out there," said McIlroy, who was tied for seventh with Lee Westwood (68).
"I felt good enough about my game that I could go out there and post a good one today and at least give myself a chance going into tomorrow."