Louis Oosthuizen tied the course record with a 63 featuring an eagle at the par-4 6th to take a share of the lead at the Alfred Dunhill Championship.
"It's the one event that I've really wanted on my CV," he said. "I've come close a few times and I've messed it up a lot of times so tomorrow if I can stay calm like I did today and do the same things and give myself opportunities on the greens I think I've got a good shot.
"I've been on the bad side of this golf course for a long time. It's such a good track, you just need to hit your shots, you can't always just play away from trouble.
"There are certain holes you need to take it on and make good swings and I stuck to that today and didn't back off on tough shots and hopefully I can do the same tomorrow."
Charl Schwartzel made six birdies, an eagle at the par-5 15th and a bogey for a 65 and his share of the lead at 15-under.
“We’ve been friends for a long time and we’ve played this game for a long time," Schwartzel said of Oosthuizen. "I don’t think we’ll treat it any other way than just trying our best and let the outcome be what it will.
"We're both playing well so it probably comes down to the guy who makes the least mistakes tomorrow.
"I'm just having so much fun being healthy. You don't realise how much injuries hamper you when you've got them because you just sort of work around them.
"All of a sudden, last week and this week there has been nothing and I can free flow and hit the ball like I used to."
Fellow South African Christiaan Bezuidenhout shot a 69 featuring four consecutive birdies from the 10th for a share of third place at 10-under.
England's Andy Sullivan carded four birdies, an eagle at the par-5 18th, a double bogey at the par-3 7th and a bogey for a 69 and his share of third place.
