Troy Merritt carded a record-equalling 61 on day two of the RBC Heritage in South Carolina to take a four-shot lead into the weekend.
The American, 29, dazzled by sinking 10 birdies in a bogey-free round to tie the course record at Harbour Town Golf Links with a 10-under-par showing.
In doing so, Merritt, who sits on 12-under-par, snatched the headlines from recently-crowned Masters champion Jordan Spieth, who carded a nine-under 62 to move to six-under for the tournament.
Merritt is being pursued by the reigning champion at Hilton Head, however, as Matt Kuchar shot 66 to move four strokes behind him, level with John Merrick.
Graeme McDowell, who took an overnight lead into Friday's session along with Matt Every, could only manage a 69 to fall five shots behind.
Spieth is one of five players in a tie for fourth ahead of Saturday, with Louis Oosthuizen, Jerry Kelly, Kevin Streelman and Every on six-under.
