Sergio Garcia has been pegged back on the second day of the Nedbank Golf Challenge after a stunning back nine from Louis Oosthuizen.
Spaniard Garcia, looking for back-to-back victories after triumphing at Valderrama, shot an eight-under-par first-round 64 to lead by four but goes into the weekend just one ahead of home favourite Louis Oosthuizen.
The South African came home in 32, with an eagle and two birdies on his back nine to card a five-under-par 67.
Garcia did extend his lead to five shots with birdies at the first two holes but had to sign for a one-under-par 71 after three bogeys in the last six holes at Sun City.
Australia's Jason Scrivener, who had been lying tied fifth after the first day, has dropped down to 29th place after posting a 76, leaving him one over for the tournament and level with compariot Lucas Herbert, who shot a second-round 69.
Garcia, who is nine under par, said on europeantour.com: "The course is tough. It's not every day you're going to go out there and shoot 64, it doesn't work like that. I feel like I played quite well.
"I stayed positive, I stayed calm. I wanted to shoot something below 70 and I felt like I had a chance of doing it, unfortunately it didn't work out but we're still in the lead. It's good."
A double-bogey at the eighth was the only blemish on Oosthuizen's card of 67, with his round also including three birdies in the first four holes, an eagle at the 10th and further birdies at 14 and 15.
Finn Mikko Korhonen sits third, three shots off Garcia, with English pair Lee Westwood and Aaron Rai, South Africa's Dylan Frittelli and Ireland's Shane Lowry a further two shots back on four under.
Rory McIlroy, who needs a top-two finish to keep his Race to Dubai hopes alive, is one under par after a second-round 71.