Charles Warren reeled off 10 birdies as he shot 62 to lead by two shots after the first round of the Chrysler Classic of Greensboro in North Carolina.
Warren's 10-under-par round matched the course record in favourable conditions at the Forest Oaks course.
"That's as close to a perfect round as I've ever played," Warren said. "I was hitting the ball exactly where I wanted and I felt like I was going to make every putt.
"I'm not going to tell you I could have shot 59, but if I was ever going to shoot 59, today would have been the chance."
Warren, who is a lowly 100th on the PGA Tour money list, is in his second season on the Tour after previously playing in 1999.
Behind Warren, KJ Choi carded a 64, while DJ Trahan shot 65.
Sergio Garcia, the top-ranked player in the field on the world standings, is in contention after a 69, alongside England's Justin Rose.
