Luke Donald's quest to regain the world number one spot was boosted by an impressive seven-under-par second round at the Zurich Classic of New Orleans on Friday.
The 34-year-old needs to finish in the top seven at Avondale to move back above Rory McIlroy and take the top ranking.
That looked unlikely after Donald fired a one-over-par 73 on Thursday which left him eight shots adrift of the leaders at the Louisiana venue.
However, he stormed back into contention in the second round, kicking off with a birdie at his opening hole - the 10th - before adding four further birdies and an eagle two at the par-four first.
The effort moved Donald to six under par, six shots off the lead, held by Jason Dufner.
Dufner, beaten in a play-off in last year's USPGA Championship, also managed a round of seven under par.
The American capped a bogey-free round with an eagle on the par-five 18th to reach 12 under and establish a one shot lead over Russell Knox, John Rollins and Ken Duke.
Knox, a 26-year-old who was born in Inverness but now lives in Florida, followed his opening round 69 with a 64 which contained an eagle, seven birdies and a bogey.
A further shot back on 10 under were Greg Chalmers, who also fired a 64, Steve Stricker and Ernie Els.
Defending champion Bubba Watson had his second straight 71 to make the cut by a stroke in his first tournament since his Masters win, with Northern Ireland's Graeme McDowell joining him on two under after a disappointing second round of 73.
Brian Davis was alongside Donald on six under, while fellow Englishmen Greg Owen and Justin Rose were a further shot back.
However, a second round 69 was not enough to see Carshalton-born, Alabama-based Gary Christian make the cut.
Collated second round scores & totals in the USPGA Tour Zurich Classic of New Orleans, TPC of Louisiana, Avondale, Louisiana, United States of America
(USA unless stated, par 72):
132 Jason Dufner 67 65
133 John Rollins 67 66, Ken Duke 65 68, Russell Knox (Sco) 69 64
134 Steve Stricker 66 68, Ernie Els (Rsa) 66 68, Greg Chalmers (Aus) 70 64
135 Camilo Villegas (Col) 69 66, Graham Delaet (Can) 68 67, Cameron Tringale 65 70
136 Daniel Chopra (Swe) 66 70, Bobby Gates 71 65, Rocco Mediate 71 65, Rickie Fowler 71 65
137 Chris Stroud 66 71, Kris Blanks 69 68, Tim Herron 69 68, Erik Compton 69 68, Kyle Reifers 69 68, Ben Curtis 67 70, Charles Howell III 71 66
138 Brian Davis (Eng) 71 67, Scott Piercy 72 66, James Driscoll 73 65, Jonas Blixt (Swe) 68 70, J.B. Holmes 71 67, Luke Donald (Eng) 73 65, Daniel Summerhays 68 70, Stuart Appleby (Aus) 69 69
139 Seung-yul Noh (Kor) 70 69, Jeff Overton 72 67, Ryan Palmer 72 67, Greg Owen (Eng) 70 69, Fred Funk 72 67, William McGirt 70 69, Alex Cejka (Ger) 70 69, Mark Anderson 69 70, Justin Rose (Eng) 72 67, Miguel Angel Carballo (Arg) 69 70, K J Choi (Kor) 71 68
140 Jason Kokrak 70 70, Vaughn Taylor 69 71, Brian Gay 70 70, Michael Bradley 72 68, Colt Knost 70 70, David Toms 72 68, Danny Lee (Nzl) 72 68, Webb Simpson 68 72, George McNeill 70 70, Briny Baird 69 71
141 Chris Di Marco 71 70, David Hearn (Can) 68 73, Will Claxton 72 69, Chris Couch 72 69, David Duval 72 69, J J Henry 69 72, Hank Kuehne 71 70, David Mathis 72 69, Jimmy Walker 70 71, Troy Kelly 69 72, Tommy Biershenk 74 67, Patrick Reed 71 70
142 Charley Hoffman 69 73, Garth Mulroy (Rsa) 70 72, Geoff Ogilvy (Aus) 76 66, Matthew Jones (Aus) 72 70, Peter Hanson (Swe) 74 68, Brendon De Jonge 73 69, Graeme McDowell (Nirl) 69 73, John Merrick 72 70, John Senden (Aus) 72 70, Lucas Glover 70 72, Gavin Coles (Aus) 72 70, Bubba Watson 71 71, Kevin Streelman 69 73, Alexandre Rocha (Bra) 72 70, Mathew Goggin (Aus) 70 72, Scott Verplank 69 73, Tommy Gainey 73 69
Missed the cut:
143 Scott Dunlap 73 70, Bill Lunde 72 71, John Peterson 71 72, Chez Reavie 74 69, Edward Loar 72 71, Blake Adams 73 70, Bob Estes 69 74, Tim Petrovic 75 68, Brandt Jobe 72 71, Billy Horschel 74 69, Kevin Kisner 72 71, Michael Putnam 70 73, Brian Harman 70 73, J.J Killeen 72 71, Joey Mclister 75 68, Cameron Beckman 73 70
144 Chris Kirk 74 70, Pat Perez 74 70, Marco Dawson 72 72, Martin Flores 74 70, Retief Goosen (Rsa) 73 71, Gary Christian (Eng) 75 69, Harris English 72 72, Jamie Lovemark 77 67, Ricky Barnes 75 69, Billy Hurley III 74 70, Jeff Maggert 71 73, Trevor Immelman (Rsa) 72 72, Josh Teater 74 70
145 Rodney Pampling (Aus) 71 74, Nick O'Hern (Aus) 71 74, Steve Wheatcroft 74 71, Keegan Bradley 73 72, Sung-hoon Kang (Kor) 71 74, Justin Leonard 74 71, Matthew Every 72 73, Brendon Todd 73 72, Roberto Castro 74 71, Stephen Ames (Can) 70 75
146 Jerry Kelly 73 73, Chad Collins 72 74, Steve Flesch 73 73, Roland Thatcher 71 75, Andres Romero (Arg) 72 74, Troy Matteson 72 74, Jason Bohn 74 72
147 Bud Cauley 71 76, Nick Watney 74 73, D.A. Points 76 71, Hunter Haas 76 71
148 Patrick Sheehan 72 76, Bryce Molder 76 72, John Mallinger 71 77, Nathan Green (Aus) 71 77, Ben Crane 77 71, Stephen Gangluff 76 72, Richard H. Lee 72 76, Carl Pettersson (Swe) 72 76, D.J. Trahan 78 70
149 Spencer Levin 72 77, Phillip Hui 77 72, Joe Ogilvie 77 72, Steven Bowditch (Aus) 77 72
150 Scott Brown 74 76, Ted Potter, Jr. 73 77, David Byrne (Can) 78 72, Ryuji Imada (Jpn) 77 73, Tom Pernice Jnr. 73 77
151 Robert Karlsson (Swe) 79 72
153 John Daly 73 80, Kyle Thompson 80 73
154 Derek Lamely 78 76
155 Jake Narro 77 78
157 Scott Stallings 80 77
WD: Angel Cabrera (Arg) 75, Charlie Beljan 77, Matt Bettencourt 74
DQ: Joe Ogilvie 77 72
