South Korea's Kang Sung scorched the Tournament Course at the Golf Club of Houston on Friday, firing a nine-under par 63 for a record-setting second-round lead at the Houston Open.
The 29-year-old, who entered the week ranked 202nd in the world, opened the second round one shot off the lead held by American Rickie Fowler.
He produced seven birdies and an eagle at the par-five eighth hole, where he rolled in a 30-footer.
Kang's 16-under total of 128 broke the 36-hole tournament record by a stroke.
His six-stroke advantage heading into the weekend is the largest 36-hole lead on PGA TOUR this season, and the largest ever at the Houston Open.
Americans Hudson Swafford and Russell Henley both carded 67s to share second on 134.
Fowler's one-under 71 -- which included six birdies as well as three bogeys and a double-bogey -- left him alone on 135, one stroke in front of Zac Blair and Aaron Baddeley.
"I putted pretty good yesterday, putted really good today," Kang said. "Plus I teed off the first off, and the greens are just pure, nobody really had them. The putter just kept making the putts."
Kang finished equal 18th at last year's US Open in his only major start, but hasn't posted a victory since the 2013 Korean Open.
A victory on Sunday would see him grab a last-gasp berth at the Masters, the first major of the year that tees off next Thursday at Augusta National.
"It's not in my head," Kang said of that tantalizing possibility. "I'll go play. Whatever happens, happens."
Fowler arrived at the 15th tee just four behind Kang. But he dropped three shots in two holes with a double bogey at 15, and a bogey at 16.
A raft of highly ranked players failed to make it to the weekend of the final Masters tuneup.
That included fifth-ranked British Open champion Henrik Stenson, sixth-ranked Jordan Spieth and seventh-ranked Adam Scott.