Marc Leishman has made an astonishing 10-birdie start to the BMW Championship at Conway Farms near Chicago to seize the lead in the PGA Tour's penultimate playoff tournament.
The Australian, who has had his best-ever season, carded a nine-under par 62 to lead by a shot, while Jason Day also fired with a 64 to take a share of second place.
It was a stellar day for the Aussies, with Queenslander Cameron Smith also on the leaderboard at five-under.
Leishman is already seventh in the season-long points race for the Fedex Cup, with its $US10 million bonus prize to be handed out in Atlanta next week, and he is projected to leap to fourth place if he wins in Chicago.
The 33-year-old from Warrnambool on Victoria's south-west coast putted the lights out; most of his birdies were from close range, although he bombed one from seven metres at the ninth hole.
His day began with a birdie from two metres at the par-four first hole, then he picked up shots at the third and fourth holes with brilliant iron shots, dropped a shot from the greenside bunker at the par-three sixth hole, then rattled home three consecutive birdies from the seventh to ninth holes.
Four birdies on the back side and three pars to close gave him the lead in the $US 8.75 million tournament, the third of four playoff events and restricted to the top 70 players on tour.
Leishman is already sure to go into the top 30 who contest the Tour Championship next week; it is just a matter of whether he can contend for the Fedex Cup as well. He would be the first Australian to win the $US10 million bonus, scooped up by Rory McIlroy last year.
"I played well,'' he told PGA Tour Radio afteward. "I hit the ball well which is obviously what you have to do to shoot that score, but more importantly, putted well. I made the opportunities that I gave myself and I'm happy with the start.''
Leishman won at Bay Hill earlier this year and was third behind Justin Thomas at the Dell Technologies Championship at last start, bringing his prizemoney for the year pasat $US 4 million. Importantly, he says his putter is working a treat.
"I think it just gives you confidence when you play golf and all you're thinking about is making birdies. It's a lot easier than thinking about just not making bogeys.''
Day's first outing with his new caddie Luke Reardon was productive; the former world No. 1 had six birdies and an eagle in his opening 64, having parted ways with longtime caddie Col Swatton this week.
He is tied-second with American Charley Hoffman, while Jordan Spieth, the Fedex Cup leader, is also in the mix at six-under par on a low-scoring day.
Smith's round was even more significant for him. Sitting at 56th in the Fedex Cup rankings, he needs to finish in the top four this week to continue on to the Tour Championship.