Chris Gotterup overcame a bout of nerves to stretch his lead to four strokes on Saturday at the Myrtle Beach Classic, where he's chasing his first US PGA Tour triumph.
"Definitely I got off to a good start on the scorecard but definitely was a little shaky. I was feeling it," said the 24-year-old American, who is making just his 27th career PGA start.
He had seven birdies with just one bogey in his six-under-par 65, which gave him an 18-under total of 195 at Dunes Golf and Beach Club in the South Carolina vacation haven.
Gotterup, who started the day with a one-shot lead was four strokes clear of South African Erik van Rooyen, Spain's Jorge Campillo and Scotland's Robert MacIntyre.
He birdied two of his first three holes and after saving par from a bunker at the eighth birdied the 10th, 11th and 13th before his lone bogey of the day at 14.
He responded with birdies at the 15th and 18th, calling his birdie at the last "huge".
"I was kind of in not a great spot over there on the right, but hit a great shot and finished it off with a really nice putt," Gotterup said.
MacIntyre, a two-time DP World Tour winner who started the day one adrift, opened with a bogey at the first. But his four birdies on the back nine included three in a row at 15, 16 and 17 for a three-under 68 and a 14-under total of 199.
Van Rooyen climbed the leaderboard with a bogey-free six-under 65 while Campillo had an eagle and five birdies to counter a bogey and a double-bogey in his four-under par 67.
Gotterup, ranked 284th in the world, said despite his big cushion he'll be under pressure on Sunday, but he embraced the opportunity.
"I practiced all those days at home for a day like tomorrow," he said. "It's going to be hard. There's a lot of good guys behind me. I'm going to have to bring it."
The tournament is played opposite the elite signature-level event at Quail Hollow in North Carolina.