Matthew Fitzpatrick maintained his two shot lead at the turn but he had an elite chasing pack gathering behind him on day three of the WGC-FedEx St. Jude Invitational.
The Englishman turned in 33 to get to 11 under at TPC Southwind but he had World Number One Brooks Koepka, four time Major Champion Rory McIlroy and three time Rolex Series champion Jon Rahm breathing down his neck.
Fitzpatrick has some serious pedigree of his own with five European Tour wins but he is seeking a first World Golf Championships victory this week.
Defending champion Justin Thomas and Australian Marc Leishman were at eight under, a shot clear of Tommy Fleetwood, Thorbjørn Olesen, Billy Horschel and Bubba Watson.
There were plenty of low scores around in perfect conditions and Rahm made a flying start to quickly join the lead.
The Spaniard put an approach to tap-in range on the second to get within one of Fitzpatrick and while the leader birdied the same hole from five feet to re-establish his two shot cushion, Rahm got on the green at the par five third and holed a 16 footer for eagle.
Fitzpatrick hit a branch with his tee shot on the par five and then almost found the water with his second, surrendering a bogey to slip to nine under alongside a charging McIlroy.
The Northern Irishman hit an excellent approach into the first and took advantage of the third before making a hat-trick of gains before the turn. 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.
Koepka was the next man to join the group a shot off the lead, holing a 30 footer on the seventh to go with birdies on the second, third and ninth as he turned in 31.
Rahm then missed the green at the sixth for a first bogey of the day and there was 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 was not there for long as Fitzpatrick hit a stunning approach into the seventh to join him in double figures.
Rahm then three putted the eighth and the leading duo were two clear of a group of five players.
Ian Poulter had birdies on the second, third and sixth, Horschel sandwiched a bogey on the seventh with gains on the third and ninth, and Thomas picked up shots on the first, second, eighth, tenth, 12th and 13th to go with a bogey on the fourth.
They were soon three back as Fitzpatrick put his tee shot on the par three eighth to 12 feet to reclaim the solo lead.
McIlroy recovered from his bogey with a tee shot to five feet on the 14th and Rahm also bounced back from 12 feet on the ninth.
A Koepka three putt on the 13th then put Fitzpatrick back into a two shot lead.
Leishman turned in 33 but was still well back before he sandwiched a chip-in eagle on the 16th with birdies on the 14th and 17th.
Horschel dropped a shot on the tenth to slip back, while Poulter surrendered a double bogey on the 12th after finding the water.