Americans Kelly Kraft, Jason Dufner, Zac Blair and Mark Hubbard, England's Harry Hall and Kim's countryman Sung Kang all share third spot at six under, with another four players tied for ninth a further stroke back.

Australian Cam Davis is in a bunch at four under, five shots behind Herbert, who reckons he was merely shaking off the rust after taking time out following his missed cut at the British Open in July.

"Golf's been getting me down pretty hard this year," he said.

"It was just a tough stretch there where I had a lot going on both in my life and on the golf course as well.

"Yeah, I missed the cut at The Open, I didn't really want to think about golf or talk about golf for about a good month there. Just needed to get away from the game and refresh everything.

"It sucked, I'd love to be here or up on the FedExCup standings as we speak, but hopefully taking that good break, refreshing, have a little reset gives me a better chance to play well in the big events next year."

Herbert was only one under through a third of his round before catching fire on the greens to pick up eight shots in his last 12 holes.

"Found a little groove there," he said.

"It felt like anything I did poorly seemed to work out nicely for me and the good shots got rewarded as well.

"I've only been back on the tour about a week now, so everything kind of feels like an adjustment out there at the moment. Still feel like I'm knocking the rust off a little bit."

At two under, Harrison Endycott and Cameron Percy are the next-best Australians behind Herbert and Davis.

Greg Chalmers posted an even-par 72 but Aaron Baddeley disappointed in his milestone 500th PGA Tour start, opening with a one-over 73 to be languishing in a tie for 106th.

Geoff Ogilvy, at four over, is almost certain to miss the halfway cut.

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