Brooks Koepka finished the front nine with a hat-trick of birdies to re-establish a two-shot lead as the US PGA Championship was set for a dramatic conclusion at Bellerive Country Club.
The two-time defending US Open champion entered the day with a two-shot cushion and turned in 33 to get to 14 under but he had a high-class pack trying to deny him a second Major Championship of the season in St Louis.
Defending champion Justin Thomas was 12 under, one shot clear of 14-time Major winner Tiger Woods, Belgian Thomas Pieters and Australian Adam Scott.
Spaniard Jon Rahm was then at ten under, a shot ahead of countryman Rafa Cabrera Bello, England's Tyrrell Hatton, Open champion Francesco Molinari and Ireland's Shane Lowry.
Woods was completely dialled-in with his irons in the early stages, putting an approach to seven feet on the first but missing his birdie putt.
He made no such mistake on the second as he holed from four feet and when he put his tee-shot on the par-three third to half that distance, he was into double-figures and just two back.
That was soon three back, however, as Koepka rolled home an eight-footer on the opener to extend his advantage.
Thomas had hit a beautiful approach into the first for a birdie and he made another on the fifth from eight feet to join Woods - who made a smart par save on the fourth - in second.
The World Number Two was putting beautifully and a 15-footer on the seventh had him within two and soon into a share of the lead.
Koepka three-putted the fourth and when he found the right rough twice on the next, it was back-to-back bogeys.
A Thomas three-putt on the ninth handed Koepka the solo lead back and he extended his advantage back to two shots with a ten-footer on the seventh.
Thomas redeemed himself on the greens from 20 feet on the tenth and made a sensational up-and-down after going a long way left off the 11th tee to share the lead.
Parity would not last for long, though, as Kopeka made it back-to-back birdies on the par five eighth.
A lovely approach into the ninth then moved him to 14 under and into a two-shot lead at the turn.
Woods had bogeyed the sixth but he had the crowds going wild again before the turn when he got up and down from a bunker for a birdie on the eighth.
His tee-shot on the next found a cart path but he bent an approach to 11 feet to get to 11 under.
Pieters turned in 33 with birdies on the first and eighth but really came to life on the back nine after he chipped in on the 11th, holing from 11 and 15 feet on the 14th and 15th to move into a tie for third.
Scott had bogeyed the first but he made a 14-footer on the seventh and then made the most of the eighth.
Rahm bogeyed the fourth but then made back-to-back birdies on the seventh and eighth to turn in 34.
Playing partners Rafa Cabrera Bello and Tyrrell Hatton both carded bogey-free rounds of 64 to set the clubhouse target alongside Molinari and Lowry, who had played 13 and 12 holes respectively.
