Brooks Koepka turned in 32 to open up a two shot lead over Rory McIlroy on the final day of the WGC FedEx St. Jude Invitational.
McIlroy entered round four at TPC Southwind with a one shot lead as the two four time Major champions went out together in the final group on a Sunday for the first time in their careers but it was advantage Koepka when he moved to 14 under after nine holes.
The American may have those four Majors to his name but he has never won a World Golf Championships title, while McIlroy is going in search of his third.
McIlroy - who turned in 35 with nine pars - is also seeking to join Darren Clarke on 14 European Tour wins and equal the record of victories for a Northern Irishman.
Spaniard Jon Rahm and American Webb Simpson were both at 11 under, a shot clear of England's Matthew Fitzpatrick and another home favourite in Bubba Watson.
Koepka got up and down to save par at the second and got up and down again on the par five third to join McIlroy at 12 under.
The overnight leader played a beautiful pitch and looked certain to follow him in but missed his own birdie chance from five feet.
Rahm had played a beautiful long bunker shot on the third to set up a birdie and when he holed a 19 foot putt for another gain on the sixth, he was at 11 under.
That was soon two back, however, as Koepka put an approach to five feet at the fifth to take the solo lead.
The leader now had the bit between his teeth and a 20 foot putt on the sixth moved him two ahead as McIlroy made it six pars in a row.
Simpson had holed from 27 feet for an eagle on the third and added a gain on the sixth but dropped a shot on the ninth to turn in 33.
Another long putt on the tenth had him back into double figures before he put his tee shot on the par three 11th to tap-in range to join Rahm at 11 under.
Watson started with a hat-trick of birdies but followed them with nine pars, while Fitzpatrick bogeyed the seventh and birdied the ninth in his first ten holes.
Tommy Fleetwood and Marc Leishman were then at nine under, one shot clear of Alex Noren.