Los Angeles - Justin Thomas, limbering up for his PGA Championship title defence, fired a one-under par 69 on Sunday to win the WGC Bridgestone Invitational by four strokes.
On a day when his nearest rivals were fading, overnight leader Thomas stayed steady at Firestone Country Club in Akron, Ohio, producing two birdies and one bogey and finishing with a 15-under par total of 265.
That left him four clear of American Kyle Stanley, who carded a two-under par 68 for 269.
World number one Dustin Johnson and Denmark's Thorbjorn Olesen shared third place on 270, both storming home with six-under par 64s as those who began the day with higher hopes floundered.
"I'm glad I finally played well around here," said Thomas, who claimed his first victory in an elite World Golf Championships event on a course where hasn't fared so well in the past.
The 25-year-old said he got "a little choked up" when he saw his grandparents in the crowd.
His grandfather, Paul, played in the 1960 Championship at Firestone.
"It's really cool," Thomas said. "They don't get to come out very often any more. This is my first PGA Tour win with them here, so that's pretty cool."
Northern Ireland's Rory McIlroy and England's Ian Poulter, who started the day sharing second three shots behind Thomas, both struggled.
McIlroy's five bogeys included three on the trot at the eighth, ninth and 10th. His three-over 73 left him tied for sixth on 272.
Poulter fired a four-over 74 that included a double bogey and five bogeys and left him in a group on 273.
Tiger Woods, an eight-time winner at the Firestone club hosting the Bridgestone for the last time, carded his second straight 73 to finish with a share of 31st.
His last nine holes saw two double bogeys, three bogeys, three birdies and just one par.
"I was just trying to be as aggressive as possible and fire at everything," Woods said. "It was either going to be 62 or 72 or something in the mid-70s.
"I was just going to be aggressive and see what happens," Woods said.
The tournament's final edition at Firestone offered little drama as no one got within two of Thomas.
The American, who won twice early this season before hitting a dry spell that included a missed cut at the British Open, will defend his PGA Championship title at Bellerive in St. Louis, Missouri, in the final major of the season starting Thursday.
Leading final-round scores on Sunday in the World Golf Championships Bridgestone Invitational at Akron, Ohio (USA unless noted, par 70):
265 - Justin Thomas 65-64-67-69
269 - Kyle Stanley 63-68-70-68
270 - Thorbjorn Olesen (DEN) 71-67-68-64, Dustin Johnson 69-71-66-64
271 - Brooks Koepka 66-70-68-67
272 - Aaron Wise 67-71-67-67, Anirban Lahiri (IND) 65-70-69-68, Patrick Cantlay 64-72-68-68, Rory McIlroy (NIR) 65-67-67-73
273 - Tony Finau 68-66-71-68, Kim Si-woo (KOR) 64-68-72-69, Jason Day (AUS) 65-66-69-73, Ian Poulter (ENG) 62-67-70-74
274 - Matt Kuchar 68-70-67-69, Tommy Fleetwood (ENG) 66-63-74-71, Marc Leishman (AUS) 65-69-67-73
275 - Gary Woodland 67-71-69-68, Ross Fisher (ENG) 67-68-71-69, Zach Johnson 69-70-67-69, Rafa Cabrera Bello (ESP) 68-67-69-71, Rickie Fowler 63-74-65-73, Jon Rahm (ESP) 64-70-68-73
276 - Cameron Smith (AUS) 70-70-69-67
277 - Phil Mickelson 66-69-72-70, Webb Simpson 69-65-71-72, Luke List 65-68-71-73, Louis Oosthuizen (RSA) 68-66-69-74
278 - Tyrrell Hatton (ENG) 68-67-72-71, Patrick Reed 66-70-70-72