Argentinean Emiliano Grillo became the man to catch at the Perth International as 2011 US Masters winner Charl Schwartzel crashed out in an intriguing second round at Lake Karrinyup on Friday.
Schwartzel shot five bogeys in a disastrous front nine and pushed a crunch five-foot putt on the final hole wide to miss the two-over cut by one stroke.
Former world No.3 Paul Casey also had a shocker, but his first-day heroics ensured he would be there for the weekend.
Casey started Friday in a tie for fourth at five-under, and took a share of the lead early after a solid start to his round.
But after dropping five strokes in a horror six-hole stretch, Casey finished at three-over for the round to lose touch with the leading pack.
There were no such problems for world No.516 Grillo, who is outright leader at 11-under after recording a five-under 67 in his afternoon grouping.
The 20-year-old's highlight was on the 344m par-four ninth, when he holed a 96m sand wedge to post his second eagle of the day.
"I didn't see it because you cannot see the green from down there," Grillo said of the magical shot.
"But as soon as I heard the crowd, I was very happy with my caddie."
American Bo van Pelt and West Australian Jason Scrivener sit four shots off the pace at seven-under, with world No.10 Jason Dufner lurking dangerously at six-under.
Van Pelt's last visit to Australia was a forgettable one, with the 37-year-old missing the cut when he played in Adelaide nine years ago.
"I was just kind of chuckling inside hoping that I didn't come over here and lay an egg like I did last time," van Pelt said.
Overnight leader Michael Hendry joins Max McCardle, Dufner and Spain's Alejandro Canizares in equal fourth, but the Kiwi was left ruing three bogeys on the back nine.
Schwartzel said he was disappointed to miss the cut.
"It was a pretty much straightforward putt and it bounced out of line," Schwartzel said.
"Nothing I can do about it.
"I figured if I could have just made the cut, you can still win the tournament.
"I don't think with the greens getting so firm the winning score is going to be that low.
"I'm disappointed the way I've played, but I've had a great time.
"It's a great city, and I would like to come back to redeem myself."