Charl Schwartzel is the leading challenger after Keegan Bradley absorbed back-to-back bogeys before equalling the course record on the opening day of the Byron Nelson Championship in Texas.
The American dropped shots at the 18th hole - his ninth - and the first, but more than made up for that with ten birdies and an eagle on his way a 60 - the first ever at the TPC Four Seasons course and only the third in the history of the event.
Sam Snead, back in 1957, and Arron Oberholser, in 2006, also have 60s at this event, but they came on different courses.
"I birdied more holes than I didn't, which is rare," Bradley said.
"It was just an explosive type of round.
"I matched up a really good ball-striking day and made everything - a really, really fun day.
"It felt easy - it always does when you play like that. It was fun.
"I made (the bogeys) back to back - a really bad bogey on one - my tenth hole. But, other than that, I didn't hit a bad shot all day."
The sparkling round came on the back of a missed cut at The Players Championship last week.
"I played really, really well at TPC," reflected the 26 year old, who carded a second round 77 at Sawgrass. "It's the first time in my career that I've ever felt like that - where I've played really well and just the numbers were so bad. But it's a good sign coming in here."
Bradley's exploits in Texas marked his lowest score on the US PGA Tour, and saw him establish a three stroke lead over Schwartzel, the South African going bogey-free through his seven under par round.
American duo Ted Potter Jnr and Harris English were in a tie for third place with Sweden's Robert Karlsson after shooting 64s, while South American duo Camilo Villegas and Angel Cabrera were alongside Ryan Palmer of the United States on five under.
