Sergio Garcia turned in 34 to open up a three-shot lead midway through the third round of the Nedbank Golf Challenge hosted by Gary Player.
The Spaniard saw a four-shot lead cut to one on Friday but he briefly restored his first-round advantage at 11 under before local favourite Louis Oosthuizen set about trying to reel him in once more in the seventh Rolex Series event of the season.
The 2010 Open Champion turned in 36 to sit two shots ahead of English duo Ross Fisher and Lee Westwood, and Finn Mikko Korhonen at Gary Player Country Club.
China's Li Haotong - who needs a win to keep his Race to Dubai hopes alive - was then six shots off the lead.
Garcia got on the green at the par-five second in two and made his birdie before he hit an approach to three feet on the third and extended his lead to three shots.
He then made an excellent par on the fourth after finding a horrible stance off the tee on the par three.
Korhonen made an excellent par save on the second after finding trouble off the tee and needing to play a smart up-and-down but dropped a first shot of the day on the fifth.
A long double-breaker on the sixth got him back to six under and he was joined there by Fisher, who was making a remarkable comeback after dropping eight shots in his last four holes on Friday.
He birdied the second and fourth and, while he gave a shot back at the eighth, he went birdie-eagle over the two par fives at the turn and then added another birdie at the 13th.
Westwood also enjoyed the ninth and tenth, going birdie-birdie to join the group in third after going birdie-bogey from the sixth.
Oosthuizen found the sand off the par-three seventh tee and dropped a shot but an approach to four feet on the ninth cut the lead back to three.
Li started with eight pars but jumped into sixth as he got on the ninth green in two and made an eagle.
South African Dean Burmester, Ireland's Shane Lowry and Englishman Matt Wallace were four under.
