Hours before his opening-round tee time at the Nedbank Golf Challenge, Louis Oosthuizen's playing status was very much in question.

He had withdrawn from the Wednesday pro-am at Sun City as he battled kidney stones, and the pain even led to a brief hospital visit in nearby Rustenberg. Due on the tee at 10:28 a.m. local time, Oosthuizen told reporters that at 3 a.m. Thursday he "didn't think I was going to tee it up."

But tee it up he did, to the tune of a 9-under 63 that gave Oosthuizen a three-shot lead as he looks to win again in his native South Africa.

"I'm very chuffed with that round," he said.

The 2010 Open remains Oosthuizen's lone PGA Tour victory, but he has won a total of nine times on the European Tour. Five of those titles have come in South Africa, including an emotional win in December at the South African Open that ended a nearly three-year worldwide victory drought.

His affinity for Gary Player Country Club in Sun City includes six straight top-15 finishes, highlighted by a third-place showing last year. He's in position for another similar showing this week after a bogey-free effort that included four birdies in a five-hole stretch on the back nine.

It's another testament to the maxim "beware the injured golfer," as Oosthuizen quickly turned a possible withdrawal into a solid lead.

"This morning was very uncomfortable, but it sort of eased in. By 6, 7 o'clock in the morning it started getting a lot better," Oosthuizen said. "This morning was just a little niggly, but I went up to the range, hit a few shots and it didn't really bother me. It was more the walking fast that got it, so I just slowed everything down and it worked nicely."

Oosthuizen is expected to be a veteran leader at next month's Presidents Cup, where he'll make his fourth straight appearance for the International team. He qualified for Ernie Els' squad thanks to a quietly solid season, one that included a runner-up finish at the Valspar Championship, T-7 result at the U.S. Open and a return to the Tour Championship for the first time since 2015.

Having turned 37 last month, Oosthuizen hasn't missed a cut since Bay Hill (a run of 17 worldwide starts) and he finished third earlier this month at the WGC-HSBC Champions in China.

Despite a hospital trip and a painful wake-up call, he now has a chance to cap that run of consistent results with yet another victory in his homeland.

"I played good at HSBC two weeks ago. I know the swing is there, the putting is there," Oosthuizen said. "I just need to be healthy to play."