By Andrew Both
SHANGHAI (Reuters) - American Dustin Johnson threatened to run away with the $8.5 million WGC-HSBC Champions tournament on Saturday, before a double-bogey at the final hole of his third round gave a glimmer of hope to the field.
Johnson pushed his tee shot into the water at the par-five 18th - which followed an earlier double-bogey - yet he still managed a six-under-par 66 in perfect scoring conditions to lead England's Ian Poulter (63), the defending champion, by three.
Soft greens and the absence of a breeze led to a birdie blitz and also a deteriorating air quality as a moderate smog hung unrelentingly over Sheshan International.
But Johnson was more bothered by his tardy finish than the smoky air, despite posting an impressive 18-under 198 total with one round left.
"I'm still a little mad from my double bogey at 18 but obviously a three-shot lead going into Sunday is good," the long-hitting Johnson, a seven-time PGA Tour winner, told reporters.
"It's a good score. I made 10 birdies, hit a lot of good shots. I'm definitely happy with what I shot, just not happy with the way I finished.
"Making two doubles, there's no excuse for that, especially the way I'm playing."
Englishman Poulter vaulted into second place on 15-under, with Northern Irishman Graeme McDowell (64) another shot behind.
McDowell's compatriot Rory McIlroy (67), Englishman Justin Rose (65) and Canadian Graham DeLaet (65) are six strokes back of Johnson in a tie for fourth.
German Martin Kaymer, the 2011 winner, shot a course record 62 but he is still eight shots off the pace in a tie for seventh.
British Open champion Phil Mickelson plunged from contention with a mediocre 72, though he still patiently signed autographs for more than 10 minutes, but only after a local official gave the crush of frenzied fans a stern warning to stop pushing.
After running off five consecutive birdies to the turn, Johnson's first double bogey come at the par-four 10th, where his tee shot finished just left of the fairway, leaving what looked like a straightforward shot to the green.
But his approach shot came up short and then he twice chipped weakly and his ball rolled back down the hill. He eventually holed a 12-foot putt to salvage a six.
At the par-five 18th, he pushed his drive into the water and couldn't be sure where it crossed the hazard line so he decided to re-tee, rather than risk any possible penalty.
Poulter also took advantage of the easier front nine, reeling off five birdies in a row from the third hole to reach the turn in 30 strokes.
"As well as I played, I felt the other guys were still going to make birdies, so I had to keep pressing," he said.
"He (Johnson) is a good player and in this form he's going to make a lot of birdies. I just need to do my thing tomorrow (Sunday) and make a lot more than he does."
McDowell also plans to keep attacking.
"I'll have to go low to even finish second," the former U.S. Open champion said.
"Very receptive greens, very pure putting surfaces, everything adds up to exactly what you're seeing, which is a score-fest."
(Editing by Patrick Johnston)