Marcus Fraser saw his lead cut to one shot as European Tour Members dominated the leaderboard on day two of the Olympic Men's Golf Competition.
The Australian came into Friday with a three-shot lead and had extended that to four as he made serene progress over his first 11 holes and looked to be taking a stranglehold over the first Olympic golf tournament for 112 years.
Two bogeys left the door ajar, though, and Belgian Thomas Pieters - who had opened his round with three birdies - bookended it with three more on the 16th, 17th and 18th to join Fraser at nine under.
A birdie on the last got the 38 year old back to double-figures and into a slender lead, but he will have to hold off an elite chasing pack if he is to claim gold over the weekend.
Open Championship winner Henrik Stenson was just two shots behind the leader after a day when heavy morning rain gave way to sunshine, with Grégory Bourdy and Justin Rose at six under, a shot clear of Rafa Cabrera Bello.
Maybank Championship Malaysia winner Fraser put approaches to three and two feet on the third and fifth to turn in 33, and when he put another iron to five feet on the 11th, he was looking totally dominant.
Bogeys followed on the next and 16th, however, before a second shot to the fringe of the closing par five set up two putts for a gain.
Fraser will go out in the final group with Stenson and Pieters on Saturday and, while he admits his game is very different to the big-hitting duo, he is looking forward to the experience.
"Those guys have completely different games and bigger games to what I have but, at the end of the day, we play 72 holes and we hit a certain amount of shots on each hole," he said. "There's more than one way to skin a cat."
"We play a game, I think the best game in the world, and it will be good fun out there with those guys.
Any time you get to play with Stenson on the weekend, you know you're doing something right - Marcus Fraser
Pieters had used his considerable distance off the tee to his advantage on day one and he did so again, sandwiching a gain at the second with birdies at the par five first and short par four third.
Another gain came on the par five tenth but bogeys followed on the 11th and 14th before he drove to the fringe of the par four 16th, put his tee-shot on the next to 15 feet, and got to the side of the last in two for three closing birdies and a 66.
"What's not to be happy about," he said. "I played well. I started out really well, I think that was the key to my round in the worst of the conditions. I knew coming to the finish there's some birdie opportunities and to take all three was a good finish."
Pieters has two wins on the European Tour but he now has his sights on an Olympic medal.
If you don't dream about it, you're never going to achieve it - Thomas Pieters
"I am thinking about it but you kind of put that beside you when you're playing and try to shoot the lowest you can."
Sweden's Stenson took advantage of the first and then got the putter going with a 60-foot birdie on the second and a remarkable 108-foot putt to save par after going in the water on the next.
He turned in 33 before a wild finish as he three-putted the 14th but then stiffed his approaches to the 15th and 16th before dropping a shot after finding sand off the tee on the 17th and birdieing the last.
Frenchman Bourdy birdied the 16th and 17th to sign for a 69, with Briton Rose - who made a hole-in-one on the fourth on Thursday - also signing for a two under par round.
Spain's Cabrera Bello recovered from a triple-bogey on third, where he got into both water and sand trouble, with birdies on the tenth, 16th, 17th and 18th in a 70.
Dane Thorbjørn Olesen was then at four under after a 68, a shot clear of Pieters' team-mate Nicolas Colsaerts and Swede David Lingmerth.
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