(CNN) -- Dustin Johnson was left frustrated after two lapses gave his rivals hope of stopping the American from running away with the biggest victory of his golf career in China.
The 29-year-old will take a three-shot lead into the final round of the $8.5 million HSBC Champions tournament in Shanghai, but two double-bogeys -- the second at his last hole -- took the gloss off a six-under-par 66 peppered with 10 birdies.
It meant that Ian Poulter's sparkling 63 in Saturday's third round put the Englishman in an even better position to emulate Tiger Woods -- the only player to defend a World Golf Championship title.
"I'm still a little mad from my double-bogey on 18," Johnson told reporters at Sheshan International Golf Club. "Obviously to have a three-shot lead going into the last day is good and I am looking forward to the challenge. I still have to play really well.
"If you told me teeing off I would shoot six under I would have taken it, but I obviously left a few shots out there. I'm definitely happy with what I shot. Obviously I'm just not happy with the way I finished."
Johnson, who had led by five at the halfway stage of the co-sanctioned tournament, is seeking to add to his seven PGA Tour victories, the last of which came in Hawaii in January.
"Making two doubles, there's no excuse for that," he said. "Especially the way I'm playing right now, it shouldn't happen. But 66 is still a good day and I did make 10 birdies, so I hit a lot of great shots."
Poulter was second on 15 under, carding an eagle and eight birdies -- five of them in a row.
"I guess the only blemish for me, which leaves a bit of a sour taste, was three-putting 17, and actually missing a couple of opportunities," said Poulter, who is chasing the $1.2 million first prize to boost his hopes of reaching the European Tour's Race to Dubai finale.
This is the second of four events leading to the 60-man shootout, with the standings headed by the PGA Tour's FedEx Cup champion Henrik Stenson.
The Swede was tied for 58th after his best round this week -- a 67 following 76 and 74.
He could be overtaken by second-placed Graeme McDowell, who is third in Shanghai after a 64 put him a shot behind Poulter.
The Northern Irishman's only major win came at the 2010 U.S. Open, where he hunted down Johnson on the final day when the U.S. Ryder Cup player also had a three-stroke advantage.
"From here it looks like Dustin is going to have to beat himself for anybody to have a chance to catch him," McDowell said.
"Race to Dubai points will be very important to me; I have a lot to play for tomorrow. If not the trophy, second place will certainly be worth my while."
Former world No. 1 Rory McIlroy shot 67 to be tied for fourth with U.S. Open champion Justin Rose and Canadian Graham DeLaet, who both carded 65.
Martin Kaymer, another player who has topped the rankings, climbed to a tie for seventh with former Masters champion Bubba Watson and another American, Boo Weekley.
The German had been on course for the holy grail of 59, but had to settle for 62 after parring his last three holes.
British Open champion Phil Mickelson was tied for 22nd after a three-bogey, three-birdie 72.
Masters titleholder Adam Scott is back home ahead of next week's Australian PGA, while world No. 1 Woods will return to action for the third Race to Dubai Final Series event in Turkey.