Zander Lombard produced the joint-best round of the penultimate day at the Joburg Open to move into a three-way share of the lead with Anthony Wall and Haydn Porteous.
As overnight leader Ross McGowan faltered on Saturday, following up a second-round 62 on Royal Johannesburg and Kensington Golf Club's West Course with a 73 on the East Course, the unheralded Lombard surged into first place with the aid of nine birdies.
A 65 lifted the South African to 15 under, a mark duly matched by Wall and Porteous, who birdied the last two holes having eagled the first.
Daniel Im, meanwhile, was one of four players two shots off the pace after going bogey free to match Lombard's third-round score.
Also on 13 under were Paul Dunne, Jacques Blaauw and McGowan, whose challenge was undermined by three bogeys and a six at the par-four seventh.
Three places at The Open are up for grabs this week - a factor that may be of particular interest to young Irishman Dunne given his stunning performance at St Andrews last year when he shared the third-round lead as an amateur.
Wall, a player at the other end of the scale in terms of experience, is aiming to end a lengthy wait for a second European Tour title - his previous success having come 16 years ago to the day at the Alfred Dunhill Championship.
"I've got a great chance [on Sunday]," said the veteran Englishman.
"But they're all good players - someone's going to be a little luckier and win, so hopefully it's me."