Rory McIlroy birdied four of his last five holes in a stunning 62 to open up a one shot lead heading into the final round of the WGC-FedEx St. Jude Invitational.
The Northern Irishman entered the day at TPC Southwind five shots off the lead but carded his lowest ever round from 103 in World Golf Championships events and his lowest of the season on the European Tour to get to 12 under and lead the way from World Number One Brooks Koepka.
The two four time Major champions will now go out in the final group on Sunday in what promises to be a scintillating final day as the tournament makes its first appearance in Tennessee.
That looked a long way away when McIlroy was three over after 13 holes on day one but since then he has made 16 birdies and a single bogey as he bounces back from a disappointing missed cut on home soil at The Open Championship.
Overnight leader Matthew Fitzpatrick carded a 69 to sit at ten under, a shot clear of Swede Alex Noren, Spaniard Jon Rahm and Australia's Marc Leishman.
McIlroy won this event in 2014 when it was played at Firestone Country Club and will be looking for a third World Golf Championships win, while Koepka will be seeking his first.
"It is exciting," said McIlroy. "He's the number one player in the world, four Majors in the last three years, he's the man right now. I got to play with him the last couple of days and I enjoyed it. I enjoyed seeing what he can do.
"The last four missed cuts that I've had, I've finished first, second, first and 12th, I'm a quick learner. We're very fortunate in golf that there's always next week, you can respond so quickly from setbacks and failures.
"Tomorrow's a new day. Whatever happened today is great but I've got to reset and try and go again tomorrow. I think it's nice that I've seen some really good golf and I've seen some putts fall. I don't know if it gives you momentum but it gives you confidence going forward."
McIlroy hit an excellent approach into the first and took advantage of the third before making a hat-trick of gains before the turn.
It is exciting. He's the number one player in the world, four Majors in the last three years, he's the man right now - Rory McIlroy
He holed a long putt on the seventh and then put his tee shot on the eighth and approach to the ninth to seven feet to turn in 30 and get to nine under.
Koepka soon joined him, holing a 30 footer on the seventh to go with birdies on the second, third and ninth as he turned in 31 and the pair were in a four way tie for the lead.
McIlroy had gone 35 holes without a bogey but he did very well to drop just one shot at the 12th as he got up and down from the sand after finding water off the tee.
Another 30 foot putt from Koepka at the 11th edged him into the solo lead but he three putted the 13th as McIlroy recovered from his bogey with a tee shot to five feet on the 14th.
Koepka put a tee shot to six feet on the 14th and then holed an 11 footer on the next to share the lead with Fitzpatrick but the Englishman stumbled in the middle of the back nine and it was McIlroy who surged ahead with a hat-trick of closing birdies.
An excellent up-and-down brought a gain on the par five 16th before he holed from 16 feet on the 17th and 27 on the last to burst ahead, with Koepka parring his way home in a 64.
Fitzpatrick had entered the day with a two shot lead and he birdied the second but bogeyed the next before gains on the eighth and ninth restored his cushion at the turn.
Another birdie followed on the 11th but he made a double bogey on the 12th after finding the water and dropped shots on the 13th and 15th before bouncing back with two birdies.
Noren made a hat-trick of birdies from the 14th to surge up the leaderboard with a 66, Rahm birdied the 15th and 18th to get back into red figures in a 68, and Leishman picked up five shots in his last five holes with the help of a chip-in eagle as he signed for a 63.
American Billy Horschel, Dane Thorbjørn Olesen and England's Ian Poulter were at eight under, a shot clear of another Englishman in Tommy Fleetwood.