Los Angeles - World number one Brooks Koepka birdied three of the first six holes on the way to winning his first career WGC title Sunday at the St Jude Invitational.
Koepka outclassed third-ranked Rory McIlroy in a last-duo duel of four-time major champions, their first ever pairing in a final round, for the victory at TPC Southwind in Memphis, Tennessee.
"It's so special. It gives me chills thinking of it," Koepka said. "It's one of my favourite stops on the tour and to win here is very special for me."
Koepka, who defended a major title at this year's PGA Championship, fired a bogey-free five-under par 65 to finish on 16-under 264 after 72 holes and defeat American Webb Simpson by three strokes.
It was the seventh career US PGA title for Koepka, the 2017 and 2018 US Open champion and 2018 and 2019 PGA Championship winner. His other prior US tour wins came in 2015 at Phoenix and in last year's CJ Cup in South Korea.
"I've been playing so well as of late," Koepka said. "Everything comes if you wait. If you keep playing well and putting yourself in contention good things will happen."
The final round brought only more frustration for McIlroy, who missed the cut last week at the British Open in Portrush, Northern Ireland, but had taken a one-stroke lead after firing a 62 on Saturday.
Koepka praised the tournament's charity, the St. Jude Children's Hospital in Memphis, saying it put the highs and lows in golf into a greater perspective.
"I've taken a trip to the hospital. It changed my life," he said. "It puts everything in perspective, how little golf means, how much life matters."
Simpson was second on 267 after a closing 64 with Australia's Marc Leishman third on 268 and McIlroy sharing fourth on 269 with England's Tommy Fleetwood and Matthew Fitzpatrick. Spain's Jon Rahm was seventh on 270 with England's Ian Poulter another stroke adrift.
Koepka sank a nine-foot birdie putt at the par-5 third hole to grab a share of the lead at 12-under, with McIlroy then missing a four-footer for birdie.
Dropping another nine-foot birdie putt at the par-4 fifth lifted Koepka atop the leaderboard, then he rolled in a tricky 20-footer for birdie at the sixth to seize a two-stroke lead at 14-under.
Koepka's uncanny iron shots continued at the par-4 10th when he landed his approach to eight feet and sank the birdie putt for a three-stroke edge on McIlroy, who opened with 11 pars before making a bogey at the par-4 12th.
Simpson eagled the third and birdied three of the first four on the back nine as well as the par-5 16th and reached the clubhouse only two adrift of Koepka.
McIlroy found his first birdie from 18 feet at the par-3 14th to reach 12-under, one behind Simpson.
But Koepka would not falter down the stretch.
He sank a clutch six-foot par putt to at 14 to stay on 15-under.
Koepka went well right and McIlroy hit into trees left off the 15th tee, but while Koepka rescued par with a tense nine-foot putt, McIlroy missed one from just inside that distance for a bogey to fall four back.
Koepka sank a 12-foot birdie putt at the par-4 17th, stretching his margin to three strokes, and he closed out with a par for the triumph.
Leading scores after Sunday's final round of the WGC St. Jude Invitational in Memphis, Tennessee (USA unless noted, par-70):
264 - Brooks Koepka 68-67-64-65
267 - Webb Simpson 69-66-68-64
268 - Marc Leishman (AUS) 69-69-63-67
269 - Tommy Fleetwood (ENG) 68-70-65-66, Matthew Fitzpatrick (ENG) 67-64-69-69, Rory McIlroy (NIR) 69-67-62-71
270 - Jon Rahm (ESP) 62-71-68-69
271 - Ian Poulter (ENG) 66-69-67-69
272 - Bubba Watson 65-70-68-69, Billy Horschel 67-66-69-70
273 - Justin Rose (ENG) 67-68-70-68
274 - Rafa Cabrera Bello (ESP) 70-71-67-66, Aaron Rai (ENG) 72-69-66-67, Patrick Cantlay 65-68-73-68, Cameron Smith (AUS) 65-68-73-68, Jordan Spieth 70-70-66-68, Patrick Reed 73-66-67-68, Justin Thomas 68-69-66-71, Alex Noren (SWE) 66-69-66-73
275 - Nate Lashley 66-70-71-68, Louis Oosthuizen (RSA) 73-69-66-67, Dustin Johnson 69-69-69-68, Li Haotong (CHN) 69-69-67-70
276 - Andrew Putnam 66-71-72-67, Adam Long 71-70-67-68, Matthew Wolff 72-70-65-69