Yet another bogey-free round lifted Noh Seung-yul into the lead of the Zurich Classic of New Orleans on Saturday evening.
Noh's blemish-free 65 allowed him to take advantage of some problems for overnight leader Ben Martin, who carded a 73 to slip down into a share of fourth, four shots off the pace.
Noh became the first player to complete 54 holes at TPC Louisiana without a bogey.
Three consecutive birdies on the 14th, 15th and 16th holes gave him the lead over Keegan Bradley, who matched Noh's round of 65 to move up to second, two shots back.
Bradley had eight birdies on his round but bogeyed the par-three ninth.
Robert Streb held steady in third place, his round of 68 leaving him three shots back.
Martin, who had led through the first two days on the back of a course-record 62 on Thursday, found the going much tougher on Saturday with bogeys on the second and ninth, his sole birdie coming on the seventh hole.
Paul Casey had the best round of the day, carding six birdies on the back nine on his way to a 64 which lifted him 20 places to a share of seventh, still five shots off the lead.
Dubliner Padraig Harrington narrowly made the cut but languishes in a share of 64th after a round of 71.