Rikard Karlberg took advantage of soft conditions to take the first-round lead at the WGC-HSBC Champions.
Russell Knox won this event on his World Golf Championships debut 12 months ago and Karlberg made a fine start in his bid to follow in his footsteps, carding nine birdies in an opening 64 to get to eight under.
Rain has battered Sheshan International Golf Club recently and continued to fall throughout the opening round, allowing for some very low scoring in Shanghai.
American Rickie Fowler was Karlberg's closest challenger at seven under, a shot clear of countryman Daniel Berger, Japan's Hideki Matsuyama and Knox, who made a confident start to his title defence.
Italian Francesco Molinari - the 2010 champion - was then at five under alongside England's Paul Casey and American Bill Haas.
Karlberg made his breakthrough at last season's 72° OPEN D'ITALIA presented by DAMIANI when he defeated Martin Kaymer in a play-off and carried that form into the new season with four top tens in his first nine events.
A run of four missed cuts in the summer stalled his campaign somewhat but the Swede is currently 28th on the Race to Dubai and heading for his best season to date.
He flew out of the blocks on Thursday, birdieing his opening four holes and adding another on the seventh to turn in 31. Further gains followed on the 11th, 13th and 14th before he put his approach on the 16th to tap-in range and made a brilliant par save on the next after a ragged tee-shot.
He was not so fortunate on the last hole, though, as he made his only bogey of the day.
"It was great," he said. "I know the kind of weather this has been, it's going to be wet and you just need to be aggressive, bomb to the tee and bomb to the pin, and that's what I did today. I had great distance control. I hit great shots all day except the last hole and it was a great day.
Everything was so easy. It was just one of those days, it was a walk in the park - Rikard Karlberg
"It felt amazing on every part of the game.
"Everything was so easy. It was just one of those days, it was a walk in the park. I committed to a lot of shots, hit them perfect, just as I wanted and I stayed aggressive on my putting all the way around, which I feel was good."
Berger had set the early pace with three birdies from the tenth and when he added further gains on the 14th and second he was in a share of top spot.
Fowler was going along beautifully, however, and after birdies on the 11th, 13th, 14th and 17th, he put his approach to the 18th inside six feet for another. He then got on the green at the par five second in two for another birdie but Berger joined him at the top with a gain from ten feet on the seventh.
Fowler then birdied the ninth to set the clubhouse target but Karlberg moved past him.
Knox also started on the back nine with four pars but came to life with four birdies in a row from the 14th before adding another on the third. A 20-foot putt on the seventh then got him into a share of the lead and he parred his final two holes.
Matsuyama made just four pars in his round with four bogeys and ten birdies, including three to finish and catapult him up the leaderboard.
Molinari won on his last time out on the European Tour as he delighted the home crowds at the Italian Open and he had birdies on the 13th, 14th, 18th, fifth and eighth in a bogey-free 67.
Richard Bland - making his WGC debut in his 396th European Tour event - was then in the group at four under along with Swede Alex Noren and Spain's Sergio Garcia, a winner here in the 2009 season.
Open champion Henrik Stenson, South Africa's George Coetzee and English trio Ross Fisher, Lee Westwood and Chris Wood were then all at three under.
World Number Three Rory McIlroy was at one under with Race to Dubai leader Danny Willett starting his week with a 74.
