American Len Mattiace birdied three of his first four holes to go 14 under par and edge ahead during the third round of the Alfred Dunhill Championship.
The 2003 US Masters runner-up, who lead with Oskar Henningsson and Robert Rock at the halfway stage at Leopard Creek Golf Club in South Africa, made a fine start to open a one stroke lead over Rock and Thomas Aiken after four holes.
Rock was two under for the day through four thanks to an eagle at the par five second, while Aiken was the day's big mover.
The South African was six under for his round after ten holes and was forming part of a strong home challenge.
Aiken`s compatriots Tyrone Mordt and Richard Sterne were 12 under after six and five holes respectively, Keith Horne was a shot further back and 2005 Champion Charl Schwartzel was ten under through seven - all of them vying to be the first home winner since Ernie Els three years ago.
England`s John E Morgan, through seven, and Swedish pair Henningsson and Johan Edfors - who had both played six holes - were also going well at 12 under as a congested leaderboard looked set to make set for a thrilling final round on Sunday.