Jason Dufner continued to set the pace but Zach Johnson also kept tabs on the leader following the third round of the Crowne Plaza Invitational at Colonial in Texas.
Dufner and Johnson are set for a virtual match play finish as they both have several strokes on the rest of the field.
Dufner shot a third round of four under par 66 to give him a one stroke advantage over Johnson whose score for the day was 65.
With Tom Gillis the next closest player at seven under the winner on Sunday should come from the leading duo.
A victory for Dufner would create history as it would make him the first player in PGA Tour history to win both North Texas events in successive weeks after his win in the Byron Nelson Championship.
Although Dufner led by two strokes at the start of the day things did not go all his way.
At one point he held a three-stroke lead only to see Johnson close the gap in the final stages of the round, including birdies at the 16th and 17th.
The 2010 champion at Colonial, Johnson has now posted 15 consecutive sub-par rounds at the course and needed just eight putts in his first nine holes and a total of 23 for the day.
Dufner said he was looking forward to his battle with Johnson after they both pulled clear of the field.
He told PGA Radio: "It's a good spot for both of us. We kind of separated ourselves (from the field) so it should be a good match.
"Zach hit a good round of golf, he's playing some nice golf. I think both of us look forward to playing tomorrow."
Dufner was pleased with the way his third round had gone.
He added: "I had a nice round. I thought I was going to get a pretty low one there with the start to the back nine.
"Unfortunately a couple of shots didn't end up distances that I wanted.
"All in all it was a pretty solid day and it was nice to finish with a birdie on 17 and it was a pretty good par on 18 from the position.
"I've really good control of my golf ball, I feel like I can hit the shots that I need, that the course kind of dictates out there."
Collated third round scores and totals, Colonial Country Club, Fort Worth, Texas, United States of America
(USA unless stated, par 70):
195 Jason Dufner 65 64 66
196 Zach Johnson 64 67 65
203 Tom Gillis 65 69 69
204 Bo Van Pelt 69 64 71
205 Ryan Palmer 68 67 70, John Huh (Kor) 70 66 69
206 Jim Furyk 69 69 68, Ryan Moore 67 69 70, Louis Oosthuizen (Rsa) 71 67 68, Kelly Kraft 71 71 64, Rickie Fowler 68 68 70, Tommy Gainey 66 67 73, Jonas Blixt (Swe) 73 67 66
207 Kevin Chappell 70 67 70, Jonathan Byrd 72 68 67
208 Charley Hoffman 69 70 69, Sung Kang (Kor) 70 69 69, Greg Owen (Eng) 69 68 71, David Hearn (Can) 71 72 65, Matt Kuchar 72 69 67, Harris English 65 70 73, Hunter Mahan 69 71 68, Corey Pavin 71 70 67, Y.E. Yang (Kor) 73 69 66
209 Brendon De Jonge 67 74 68, Chris Stroud 69 73 67, John Daly 70 69 70, Ben Crane 70 71 68, Vijay Singh (Fij) 70 69 70, Kyle Reifers 65 72 72, Ken Duke 68 75 66, Roberto Castro 67 74 68, David Mathis 71 67 71
210 Chris Kirk 71 69 70, Trevor Immelman (Rsa) 70 71 69, Bobby Gates 71 67 72, Sergio Garcia (Spa) 66 73 71, Geoff Ogilvy (Aus) 70 70 70, Carl Pettersson (Swe) 70 69 71, Tim Clark (Rsa) 70 69 71
211 Bryce Molder 72 64 75, Jerry Kelly 72 70 69, Seung-yul Noh (Kor) 70 69 72, Martin Flores 68 73 70, Greg Chalmers (Aus) 70 69 72, Blake Adams 69 72 70, J.J Killeen 72 70 69, Chad Campbell 71 71 69, Michael Thompson 69 71 71, Boo Weekley 72 71 68, Jason Bohn 70 70 71
212 Charlie Wi (Kor) 68 69 75, Kevin Na 70 71 71, John Senden (Aus) 69 71 72, Brandt Jobe 67 75 70, Will Claxton 72 69 71
213 Rory Sabbatini (Rsa) 71 71 71, Pat Perez 69 74 70, Chris Di Marco 66 74 73, John Mallinger 71 72 70, George McNeill 72 69 72, Bill Haas 72 71 70, Miguel Angel Carballo (Arg) 75 68 70, Josh Teater 70 71 72
214 Aaron Baddeley (Aus) 71 70 73, Nick Watney 71 71 72, Marc Leishman (Aus) 72 68 74, William McGirt 70 71 73, Mark Wilson 71 71 72
215 Kris Blanks 73 69 73, Andres Romero (Arg) 66 71 78, Gary Christian (Eng) 70 73 72
216 Brendon Todd 70 71 75, Gary Woodland 70 70 76, Hunter Haas 71 72 73, Edward Loar 72 71 73
217 Sang-moon Bae (Kor) 70 70 77
218 Heath Slocum 70 73 75
219 Justin Leonard 69 73 77
