SHANGHAI (REUTERS) - World No. 1 Dustin Johnson humbled Brooks Koepka in a third round shoot-out at the WGC-HSBC Champions in Shanghai on Saturday to take a six-stroke lead over his compatriot heading into the final day of the US$9.75 million (S$13.3 million) event.
Having teed off a stroke ahead of US Open champion Koepka, overnight leader Johnson pulled away from his playing partner to card a composed four-under 68 as most of his rivals battled on a breezy day at Sheshan Golf Club.
Koepka had snatched the lead with a birdie on the first hole and extended it to two strokes by the third but the 27-year-old imploded with a triple-bogey on the par-five eighth and finished the day fuming after a scratchy 73.
The long-hitting Johnson moved to a 17-under total of 199 and nothing short of miracle should stop the 2016 US Open winner from notching his third World Golf Championships title of the year.
Third-placed Henrik Stenson will tee off seven strokes behind Johnson after shooting 69, with Major winner Justin Rose (72) and Brian Harman (70) a shot further back on nine-under.
Having torn up the course with a new putter on Friday, Johnson stumbled with a bogey on the first hole to surrender the lead but hit back with a birdie on the second and proceeded to apply a blow-torch of pressure on Koepka.
Johnson drew level after birdies at the fourth and seventh, and Koepka duly crumbled at the eighth, driving into the trees on the left.
Worse was to come for Koepka, who from the middle of the fairway, put his fourth shot into a thicket of trees left of the green and had to traipse some 70 metres back to take a drop shot.
Johnson had also miscued his approach to the left but was saved from the trees by a fortunate bounce.
He then rubbed salt into Koepka's wounds by rolling in a sublime, breaking 20-foot putt for birdie.
Koepka's misery was complete when he missed his double-bogey putt from eight feet to plunge four strokes behind.
Johnson opened the door with a double-bogey on the par-four 10th but promptly slammed it shut by birdieing two of the next four holes.
Koepka battled to keep in touch but the pressure showed as he shanked his tee shot on the par-five 18th into a bunker and snapped at fans for using their mobile phones.
He then blasted his second shot out of the sand straight into the water hazard on the right, his tournament hopes sinking as quickly as the ball on the way to his third bogey.