Jason Bohn shot a stunning nine-under-par 61 to join a four-way tie for the lead after three rounds of the Greenbrier Classic.
Five birdies either side of the turn lifted Bohn to the best round of the week and his best ever, marred only by a bogey at the par-four 11th, as he joined fellow Americans Sean O'Hair and Bryce Molder and South Korea's SJ Park at the summit.
Justin Thomas, David Hearn, Danny Lee and Chad Collins are one shot back with a thrilling finish in prospect on Sunday.
Tiger Woods was over par for the first time all week, with a 71 leaving him four under for the tournament.
Starting at two under after successive rounds of 69, Bohn holed from 19 feet at the second and 15 at the fourth for birdies before a beautiful approach set up another at the sixth.
Back-to-back successes at eight and nine took him to the turn in 29 and he made it three in a row before a duffed chip at 11 threatened to stall his momentum.
However, four birdies in the last five holes vaulted him to the top of the leaderboard and he told PGA Tour Radio: "I made a 20-footer on the first for par and then just kept seeing a line, kept hitting them on the fall lines and didn't have much break on any of my putts.
"It's soft and you can attack the flags but you've got to place your ball in the right spots."
Bohn had to finish with a birdie on Friday just to make the cut and he said: "I had some good momentum, started swinging better on the back nine yesterday and it carried forward today.
"But you never know when something like that's going to happen, where you're going to shoot nine under.
"I won't be getting up too early tomorrow, so that'll be nice."
Molder had made his move with a 64 on Friday and followed it up with a three-under-par 67, the highlight a 22-foot birdie putt at the ninth which circled the hole before dropping.
O'Hair and Park shot 66, Park without a bogey on his card while O'Hair made his move on the back nine with four birdies in six holes.
Thomas matched Park's immaculate 66 while Hearn - like Molder, coming off a 64 on Friday - Lee and Collins each carded 68.
Sweden's David Lingmerth shared ninth place with Americans Brendon Todd and Jonathan Byrd on nine under, with England's Greg Owen among five players a further shot back and amateur Maverick McNealy in the group on seven under.
Woods was looking to continue a promising week and birdies at the second and seventh helped him on his way, but a dropped shot at eight was the prelude to an erratic back nine.
Birdie at 10 was negated by a double-bogey at the next and a further dropped shot at 13, and though a birdie at 15 brought him back to par for his round, a wild tee-shot at the 17th led to a bogey six and a one-over-par round.
Source: PA
