Danny Lee carded a five-under-par 65 to take a one-shot lead after the first round of the WGC-Bridgestone Invitational in Akron, Ohio.
Graeme McDowell and Jim Furyk are in a tie for second after firing four-under-par 66s, while Rickie Fowler and Justin Rose sit in a tie for fourth after carding 67s.
Reigning Masters and U.S. Open champion Jordan Spieth and world number three Bubba Watson are in a tie for 22nd after starting their campaigns with level-par 70s.
World number one Rory McIlroy was unable to defend his WGC-Bridgestone title as he continues his recovery from an ankle injury, but there were plenty of highlights even in the Ulsterman's absence.
Lee, who began at the tenth tee, came out firing from the start and made consecutive birdies before missing a 15-foot par putt at the 12th to register his first bogey.
The New Zealander made up for the dropped shot with a sensational 47-foot birdie putt at the next hole before missing a seven-foot par putt to record his second – and last bogey – of the round at the 15th.
Lee made another birdie at the 16th before adding three more on his back nine – at first, second and fourth holes.
McDowell, who sits one stroke behind Lee, enjoyed a bogey-free front nine and registered birdies at the second, third, sixth and seventh. He made his fifth birdie of the round at the 10th before faltering at the 12th, where he missed an 11-foot par putt, to register his only bogey of the round.
Alongside McDowell on four-under is Furyk, who began his round strongly with four birdies and a bogey on the front nine. The 45-year-old came close to producing a hole-in-one at the fifth when his tee shot landed just eight inches short of the cup.
Two more birdies followed at the 11th and 15th before Furyk stumbled with a bogey at the 18th.
Fowler and Rose trail Lee by two strokes after making four birdies and a long bogey in their rounds of 67.
Spieth, who sits five strokes behind Lee, began with a bogey after a missed 11-foot par putt at the second.He got that stroke back with a birdie at the fourth to take the turn at level par. He struggled to get going on the back nine too, with a bogey at the 10th followed by consecutive pars before completing his round with a birdie at the 18th.
Watson, who is level with Spieth on even-par, began with a birdie at the first before making the first of his three bogeys at the seventh. Another bogey followed at the 12th before he sunk a 22-foot putt at the 13th for his second birdie of the round.
A missed a 23-foot par putt at the 15th saw Watson register his third bogey of the day, before he wrapped up his round with a birdie at the 16th.