Shanghai - Dustin Johnson charged into a handsome six-shot lead at the $9.75 million WGC-HSBC Champions in Shanghai on Saturday after an anticipated third-round battle with close friend Brooks Koepka failed to materialise.
In breezy conditions Johnson's four-under-par 68 stretched his one-shot overnight lead on his fellow American, who shot an error-strewn 73, leaving the world number one in pole position for the final day on Sunday.
Third at Sheshan International Golf Club, on 206 overall and seven shots off the imperious Johnson, was last year's runner-up Henrik Stenson of Sweden.
American Brian Harman and Englishman Justin Rose, the Rio 2016 Olympic champion, were joint fourth.
"I'm not worried about what anyone else is doing, I've got enough to worry about with just myself," said Johnson on his mindset going into the decisive day with such a big lead.
"I'm not going to change my game plan playing no matter what Brooks does, Henrik, whoever is out there playing.
"I'm going to stick to it and hopefully execute."
Johnson and Koepka live near one another in Florida and are fishing and gym buddies.
But the niceties were left in the clubhouse and reigning US Open champion Koepka was immediately on the front foot, grabbing a birdie at the first while Johnson carded just his third bogey of the week.
That immediately wiped out Johnson's slender overnight lead and was the first of three birdies on the spin for the 27-year-old Koepka to propel him briefly into the lead.
But that was as good as it got for Koepka.
Johnson made birdies at holes two, four, seven and then at eight, where Koepka's challenge faltered badly with a horror triple bogey.
The 33-year-old Johnson, the 2013 Shanghai champion and 2016 US Open winner, made the turn having opened up a four-shot lead on his rival.
Johnson gave a subtle shake of the head after a double bogey at the par-four 10th, but Koepka failed to capitalise with a bogey of his own and Johnson was always in control after that despite the tricky wind.
Hideki Matsuyama, the reigning champion from Japan, had another poor day with a 72 to leave him firmly out of the reckoning.
Johnson identified the eighth hole as the turning point and Koepka called holes eight to 12 "a disaster".
"I don't know what happened from eight on," said a deflated Koepka, ranked 11 in the world.
"It was kind of very disappointing - very blah. I didn't really make any putts, like those momentum putts. I didn't make one of those."
Koepka also said he had been put off on the 18th hole, where he stumbled to a third bogey of the day, by multiple cameras going off.
Rose carded a 72 and similarly struggled in the wind, having started the day in tied third and still in the hunt.
"Wasn't good enough, is what it was, but it was tricky out there," he said.
"But all in all, DJ (Johnson) played great golf today and obviously stretched out a little too far ahead."
The 37-year-old at least had the consolation of a birdie at the final hole, but said he was only really chasing second behind Johnson on Sunday.
"You kind of walk away, the course didn't beat me today," he said of making a last-gasp birdie.
"I feel like that birdie can hopefully make dinner taste good and come out and try and do something special."
Leading third-round scores at the $9.75 million WGC-HSBC Champions in Shanghai on Saturday (par 72):
199 - Dustin Johnson (USA) 68-63-68
205 - Brooks Koepka (USA) 64-68-73
206 - Henrik Stenson (SWE) 68-69-69
207 - Brian Harman (USA) 68-69-70, Justin Rose (ENG) 67-68-72
208 - Kyle Stanley (USA) 71-68-69, Peter Uihlein (USA) 72-67-69, Rafa Cabrera Bello (ESP) 68-70-70
209 - Tyrrell Hatton (ENG) 68-70-71, Matt Kuchar (USA) 67-70-72, Matt Fitzpatrick (ENG) 68-69-72
210 - Paul Dunne (IRL) 67-73-70, Charles Howell (USA) 72-67-71, Kiradech Aphibarnrat (THA) 65-70-75
211 - Poom Saksansin (THA) 73-70-68, Ryu Hyun-Woo (KOR) 69-73-69, Patrick Cantlay (USA) 68-74-69, Tommy Fleetwood (ENG) 71-70-70, Bernd Wiesberger (AUT) 71-70-70, David Lipsky (USA) 69-70-72