Bill Haas and Nicolas Colsaerts posted matching rounds of 2-under 70 on Thursday and share the lead after the first round of the Nedbank Golf Challenge.
Haas and Colsaerts are both playing this event for the first time. The two are ranked 37th and 36th in the world respectively.
Lee Westwood, the two-time defending champion, opened with a 1-under 71 and was joined in third place at Gary Player Country Club by a pair of former British Open champions, Paul Lawrie and Louis Oosthuizen.
Peter Hanson, Martin Kaymer, Francesco Molinari, Carl Pettersson and Charl Schwartzel are tied for sixth at even-par 72.
Justin Rose, the 2007 runner-up, is alone in 11th at plus-1, while Garth Mulroy is last in the 12-player field at 3-over 75.
Haas, the 2011 FedEx Cup winner, birdied the par-5 second, but gave that stroke right back as he bogeyed the third. After three straight pars, he converted a birdie chance at the par-3 seventh.
Around the turn, Haas birdied the 10th and followed with a 12-foot birdie putt on the 11th to move to minus-3. He increased his lead with a birdie on No. 15 from five feet out, but trouble loomed.
Haas faltered to bogeys at 16 and 18 to drop back into a share of the lead.
"Overall, to get it to 4-under, I felt like I was doing a lot of good things. I'm happy with 2-under, but it would have been nice to shoot a couple (more under), because it's playing tough out there," Haas stated.
Colsaerts got going with a birdie on the first. He cruised to six consecutive pars from the second, then tripped to a bogey at the eighth.
The 30-year-old Belgian converted back-to-back birdie efforts at the 10th and 11th to move to minus-2. Colsaerts, who had 10 birdies in his Ryder Cup match against Tiger Woods, parred the final seven holes to end alongside Haas.
"I normally hit it very long off the tee, but around here I chose a less aggressive strategy, even when I was hitting driver. I played the same game as everyone," said Colsaerts. "The wind was quite difficult to read, and it always felt like it was coming from one side. I had difficulty with it at 18. I actually played better before the turn, and I missed a few birdie putts on the back nine."
NOTES: Only seven of the 12 players in the field have competed in this event before ... Westwood is making his fourth appearance, while Schwartzel and Rose are playing for the third time ... Westwood is the only former winner playing this week.