Defending champion Charl Schwartzel set the early clubhouse target on day two of the Alfred Dunhill Championship after posting a 68 at Leopard Creek Country Club on Friday.
Schwartzel led by a single shot after carding six birdies and a disappointing double bogey in his second round to get to ten under par.
Fellow South African George Coetzee was Schwartzel's nearest challenger on nine under after mixing nine birdies with a double bogey in his stunning 65.
The stroke’s feeling good, which makes me very comfortable - Charl Schwartzel
Home favourite Schwartzel began the day alongside Irishman Paul Dunne at the top of the leaderboard on six under after Thursday's bogey-free 66.
Starting his second round at the tenth tee, Schwartzel made consecutive gains at the 12th and 13th to take the outright lead.
After finishing his front nine with a birdie at the 18th, Schwartzel picked up another shot at the first.
He then holed his monster birdie putt at the fourth to get to 11 under before rolling in from 20 feet for another gain at the next.
But Schwartzel carded a double bogey at the seventh - his first blip of the tournament so far - to slip back to ten under, before safely parring his final two holes.
Schwartzel said: "Overall I think I played well. I gave myself a fair amount of chances and made some nice bonus putts.
"The stroke’s feeling good, which makes me very comfortable.
"I mean I’m right up there. Maybe I can hit the ball a little bit better, maybe I can time it a little bit better.
"The game is not a game of perfection, so I’ve done well with what I’ve had so far."
Also beginning his second round at the tenth, Coetzee, who shot an opening 70 on Thursday, made birdies at the 12th and 13th to get to four under.
The 30 year old carded a double bogey at the 17th but bounced back in style, notching six birdies in his next seven holes to climb up the leaderboard.
And Coetzee rolled in his 20 foot birdie putt at the ninth - his last - to get to nine under.
He said: "I made the putts that you're supposed to make and I made a couple of extra ones as well, which is always quite nice.
"You've got to hit good tee shots in these winds and if you do that you've got a pretty good chance of making birdies."
South Africans Jean Hugo and Branden Grace were in a tie for third on eight under after their second rounds, alongside Frenchman Benjamin Hebert and Sweden's Alexander Björk.
