World number 1,555 Nic Henning has missed the cut after going into the Jo’burg Open second round as leader.
Henning, the joint lowest-ranked golfer on the professional tour, carded a nine-under-par 62 opening round to equal the course record.
But the 45-year-old South African was six over at 78 on day two to end hopes of a first Tour win.
Compatriot WallieCoetsee leads on 12 under, with English golfer Simon Dyson among three players who are one behind.
He is on 11 under with South Africans Garth Mulroy and Tjaart van der Walt.
Henning, who has not managed a top-10 finish for five years, went out in 29 on the opening day, with five birdies and an eagle on the West Course at Royal Johannesburg and Kensington Golf Club in his homeland.
But it was a different story on the tougher East Course – after starting with a birdie four, he ran up six bogeys and one double-bogey and missed the cut by one shot.
Henning took 16 more shots on his second round than his first
Halfway leader WallieCoetsee, the world number 509, revealed he does not own a TV after adding a 65 to his opening 66.
“Life is so much simpler, especially without television. We’re in bed early and we read a lot of books. And we’re up early, walking on the beach before we take the kids to school,” he said.
Dyson, 37, has won six times on the European Tour but has not claimed a title for four years.
He looked rejuvenated having missed the cut in his first three events this season and with a best finish of joint 50th so far in 2015. After firing six birdies and one bogey in his 67, Dyson said he had reverted to an old set of irons.
“It’s been a while since I’ve been up there. This is the first week I’ve put my old set back in the bag and all of a sudden I’m hitting it pin high again; that makes a heck of a difference,” he said.
However, European Ryder Cup captain Darren Clarke could only card a second consecutive 72 to miss the cut by five shots.