Ben Martin shot a stunning 62 to take a two-shot lead after the opening round of the Zurich Classic of New Orleans.
The 26-year-old made the turn in 30 and, following birdies on the 10th and 11th, it looked as if he may become just the seventh man in history to shoot a 59 in a PGA Tour event.
A further birdie on 13 followed but the scoring then dried up in windy conditions and he would pick up just one further shot on 17 to move to 10 under and establish a two-shot lead over Andrew Svoboda.
Martin is yet to claim a Tour win but finished in an impressive tie for third at last week's RBC Heritage.
Svoboda registered a flawless 64 that included six birdies on the back nine.
The American carded birdies on one and eight but then found some momentum after the turn with further birdies on 10 and 11.
He also picked up shots on 13,14,17 and 18 and admitted that he felt he had played his best round of the year so far.
"It's real nice to shoot eight under today," he told Sky Sports 4.
"I'm really pleased, it's probably the best round I've played this year."
Sveboda is quietly having a break-out season after making six of 10 cuts so far and registering his first two top-25 finishes on Tour.
Sweden's Peter Hanson and Korea's Noh Seung-yul were a further shot back with American duo Erik Compton and Chad Collins on six under.
Former Open champion David Duval registered just his fourth sub-70 round in seven starts this season and then declared he felt he was ready to win again.
The American has not had a Tour win for 13 years but shot a four under par 68 and, after a few false starts before, feels he could upset the odds this week.
"Two or three years ago, I may have been thinking I could win," he told www.pgatour.com. "But looking back on it, I wasn't physically equipped. My game wasn't good enough.
"I was a little delusional about how I was playing."
He added: "I'm not delusional about it now, I know how I'm hitting the golf ball and how I'm swinging the club.
"I feel comfortable. I feel natural again. I feel like the timing is right."
Padraig Harrington was two shots behind Duval on two under, a shot clear of England's Paul Casey and Justin Rose.