Jason Dufner, who is chasing his first US PGA Tour win in 163 starts, extended his lead to two shots after firing a five-under-par 67 in the third round of the Zurich Classic.
American Dufner moved to 17-under 199, two strokes ahead of Canadian Graham DeLaet who soared into contention with a six-under 66 for 201 at TPC Louisiana in New Orleans.
South African Ernie Els (68) and American John Rollins (69) were tied for third on 14-under.
Leading Australian Greg Chalmers slipped into a tie for 12th spot on 206 after a 72 to follow his second-round 64.
Dufner, who turned 35 last month, finished with six birdies and one bogey on Saturday.
He has struggled to hold 54-hole leads in the past. He led heading into the final round of the 2011 PGA Championship but lost in a playoff to Keegan Bradley.
“I hadn’t played as well as I would like on the weekends, I have tried to identify some of the reasons why and will try to implement some of those tomorrow,” said Dufner, who also lost in a playoff last year at the Phoenix Open to Mark Wilson.
“Right now, a win would be great. Obviously I’ve been knocking on the door with a lot of solid rounds, lot of solid play last year and at the end of the year.”
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. DeLaet played just twice on the tour in 2011, making the cut at the St Jude Classic but finishing in a tie for 73rd.
“It’s exciting,” said DeLaet. “It’s the first time I’ve been in this position this deep into a tournament. I’m looking forward to the challenge.”
Masters winner and defending champion Bubba Watson 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.
In a span of just two days, Watson went from saying he wished he was at home with his family to giving himself an outside chance at a victory.
“I’m tied for 15th (actually 16th),” Watson said. “So long as I don’t choke tomorrow, I should have a good shot at it.”
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.