World number five Adam Scott held firm in blustery conditions to finish three strokes behind journeyman Matthew Guyatt after the second round of their home Australian Masters on Friday.
But Graeme McDowell crashed to a 77 on a gusty afternoon in Melbourne.
McDowell had a dream start with an eagle and a birdie on his first two holes, but racked up six bogeys and a double-bogey on the par-four sixth to tumble to four-over for the tournament.
Ducking in and out of bushes to retrieve his ball, the 2010 US Open winner also struggled on the slick greens, saying he could not remember putting worse.
"The harder I tried the worse I got and it was just one of those humbling days but hopefully that will slip in for the weekend and get two more days on this great golf course," he said after just sneaking inside the cut line at four-over.
"I need something, I either need to go and batter myself in the gym tonight or batter myself in the casino, I'm not sure which one is going to happen but probably the former." Joint-second overnight, Scott ground his way through a gusty afternoon to card a two-under-par 70 for a seven-under total of 137 and raise hope of his first tournament win this year after a frustrating season of near-misses.
"It was a tough day. The wind was pretty strong, at least two clubs I'd have to say," said the 32-year-old Scott, in outright third.
"It firmed the course up from yesterday. We had a different set of greens than we dealt with yesterday, so I had to be very careful and not try my luck too much ... I think I'm in pretty good shape." Scott fared the best of the tournament's marquee players, with title holder Ian Poulter falling five off the pace with a 70.
Joint-second with Scott overnight after plundering the sandbelt course in perfect conditions on Thursday, Briton Poulter fumed after cancelling out three birdies with three bogeys in his second round.
"I'm frustrated. I'm not going to stand here laughing, am I?" he snapped at reporters greenside.
Guyatt, a 37-year-old former Australian Rules footballer, shot a patient 69 for a 10-under total of 134 to be two strokes ahead of second-placed New Zealander Michael Hendry and enjoyed his new-found celebrity.
Trading jokes with spectators and receiving the gift of a football from one of the local code's top players, Queenslander Guyatt only returned to professional golf this year with the help of an elderly benefactor after a five-year hiatus to work at a Brisbane golf club.
"He just about fell over," Guyatt said of his backer's reaction when he learned he was leading the tournament.
"He's 78 years of age so I was just hoping he hadn't had a heart attack." The mental strain of leading into the weekend would be the ultimate test, Guyatt said.
"That's the battle that players in my position face ... The belief that you've got enough game - the belief that you're good enough. I think I'm starting to get there."