American Jason Dufner, who is chasing his first US PGA title, extended his lead to two shots after firing a five-under 67 in the third round of the Zurich Classic in New Orleans.
Dufner moved to 17-under par 199, two strokes ahead of Canadian Graham DeLaet who soared into contention with a six-under 66 for 201 at the TPC Louisiana.
South African Ernie Els (68) and American John Rollins (69) were tied for third on 14-under 202.
Leading Australian Greg Chalmers slipped into a tied for 12th spot on 206 after a 72 to follow his second round 64.
Dufner is looking for his first win in 163 starts. He has led after 54 holes two times previously but failed to earn a victory both times.
He led the 2011 PGA Championship before losing in a playoff and tied for third at the 2009 Canadian Open after leading at the end of three rounds.
DeLaet shot his lowest round since firing a 63 in the opening round of the Sony Open. Before the Sony, he sat out half a year while recovering from back surgery.
Ryan Palmer tied the course record with a 64, becoming the third player to shoot the score this week.
He was tied for fifth on 13-under 203 with Cameron Tringale (68) and Steve Stricker (69).
Masters winner and defending champion Bubba Watson also rocketed up the leaderboard with a seven-under 65. Watson, who made the cut by one stroke on Friday, has a share of 16th place at nine-under.
England’s Luke Donald (66) was 12-under and tied for eighth with Ken Duke (71). Donald needs a solo finish of seventh or better to regain the first spot in the World Golf Rankings.