Russell Knox two shots off leader Rikard Karlberg in Shanghai
Scotland's Russell Knox was delighted to make a superb start to the defence of his title in the first round of the WGC-HSBC Champions in Shanghai.
Knox was 20 under par in winning his first European Tour title last year and carried on where he left off on Thursday as he tries to become only the second player after Tiger Woods to retain a World Golf Championships title.
The 31-year-old carded a bogey-free 66 at Sheshan International to finish six under par, two shots behind Sweden's Rikard Karlberg.
American Ryder Cup star Rickie Fowler was a shot behind Karlberg after a flawless 65 and the group of Knox, Fowler and Paul Casey were a combined 18 under par after Casey carded a 67 which featured an eagle, four birdies and the group's only bogey of the day on the 11th.
After starting on the back nine, Knox followed four straight pars with the same number of birdies in succession from the 14th, before picking up further shots on the third and seventh.
"I'm always thrilled with no bogeys and my first round is never my strongest round," said the world number 20, who was born in Inverness but is based in Florida. "So to get off to a flyer and shoot six under, I'm delighted.
"I didn't put any pressure on myself. I didn't feel overly tight out there, so I was proud of myself to kind of relax and enjoy it. It can only be your first defence once, so I'll make sure I'm going to have a good time the next three days.
"The conditions were just like this on Sunday last year, very dark and dreich, as the Scots would say, with a little mist and rain. The course played long today, which is fine for me.
"If it's lift, clean and place (preferred lies), as long as I'm on the fairway I can compete around here."
Knox was joined on six under par by American Daniel Berger and Japan's Hideki Matsuyama, who carded 10 birdies and four bogeys in his 66.
Former champion Francesco Molinari and Bill Haas were both five under par alongside Casey, with Sergio Garcia and Richard Bland part of a four-strong group a shot further back.
World number three Rory McIlroy ended the day seven shots off the pace as he chases the victory he feels is necessary to have a chance of winning the Race to Dubai for the third year running.
McIlroy is more than a million points behind Masters champion Danny Willett, who has a lead of more than 400,000 points over Open champion Henrik Stenson, who carded an opening 69.
Willett battled back from a nightmare start to return a 74, three bogeys and a dou ble bogey in the space of four holes taking the Masters champion to the turn in 41 before birdies on the second, third and ninth repaired some of the damage.
McIlroy also started on the 10th and ended a run of six straight pars with a birdie on the 16th, although even that was something of a disappointment after driving the green on the short par four and missing from eight feet for an eagle.
And there was worse to come on the par-five 18th as the four-time major winner pushed his approach into the water surrounding the green, the resulting bogey dropping him back to level par.
A frustrated McIlroy finally got back into red figures with just his second birdie of the day on the seventh and parred the last two holes to sign for an opening 71.
Karlberg had birdied his first four holes of the day and reached nine under par after 16, only to bogey the 18th after finding sand off the tee and thick rough with his recovery.
"Everything was so easy," Karlberg said. "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.
"I hit great shots all day except the last hole and it was a great day. It felt amazing on every part of the game."