Australian Brett Rumford is the clubhouse leader at the $2 million Perth International, but world No.21 Dustin Johnson looks done and dusted after falling nine shots off the pace.
Rumford shot a seven-under 65 on Saturday to take a share of the lead with JB Hansen.
The West Australian was on track for a course-record 64 before missing his three-foot putt on his final hole.
Overnight leader Peter Hedblom, who needs to win the tournament in order to keep his European Tour card, is now two shots off the pace.
Pre-tournament favourite Johnson shot a three-over 75 on Saturday to lose touch with the leading pack.
Defending champion Bo van Pelt is lurking at four-under, while West Australian Jason Scrivener and Korea’s Jin Jeong are just one shot off the lead at six-under.
Australian Rohan Blizard was singing in the rain after snaring a hole-in-one at the par-three 17th.
But countryman David McKenzie had even more reason to celebrate after his hole-in-one on the par-three eighth won him a car.
England’s 12-time European Tour winner Paul Casey missed the cut on Friday after finishing at three-over from his two rounds.