Former Open champion Louis Oosthuizen will take a three-shot lead into Monday's final round of the Deutsche Bank Championship after a brilliant 63 at TPC Boston.
Oosthuizen began the day one shot behind playing partner Rory McIlroy and watched as the world number one birdied the first two holes.
However, the South African also picked up a shot on the par-five second and then fired seven birdies in succession from the fourth.
That meant a tournament-record 29 on the front nine and although his birdie on the 10th was followed by six pars and a bogey, a closing birdie on the par-five 18th saw the 29-year-old finish 19 under par.
"Louis put on a display right there," McIlroy said. "I was delighted when I got the honour back on the 12th tee."
McIlroy returned a 67 to finish three behind on 16 under, adding: "I've come from farther behind before.
"It's going to be an interesting day tomorrow."
Dustin Johnson continued his quest for a Ryder Cup wild card with a 65 to move into third place on 13 under alongside Tiger Woods, who carded a 68.
Oosthuizen, who once shot a round of 57 on his home course in Mossel Bay in South Africa, said: "This felt similar, except that I was playing with friends and not in a big tournament like this one.
"Every putt had perfect speed. I told Rory, 'Sorry, but you've got to take it when you can."'
Despite being six shots off the lead, Woods has not given up hope of victory after a host of low scores this week.
"I'm going to have to put together one of those rounds," Woods said. "It won't surprise me if somebody shoots eight or nine under par tomorrow because of where the pin locations are.
"Somebody is going to go out there and do it. It may be early, it may be late, who knows? But hopefully, I'm one of those guys."
Collated third round scores & totals (USA unless stated, par 71):
194 Louis Oosthuizen (Rsa) 66 65 63
197 Rory McIlroy (NIrl) 65 65 67
200 Dustin Johnson 67 68 65
202 Bryce Molder 65 69 68, Tiger Woods 64 68 70, Ryan Moore 64 68 70
203 Charley Hoffman 67 67 69, Jason Dufner 67 66 70
204 D.A. Points 68 65 71, Phil Mickelson 68 68 68, Jeff Overton 64 71 69, David Hearn (Can) 67 69 68, Brandt Snedeker 69 70 65
205 John Senden (Aus) 66 69 70, Webb Simpson 69 70 66
206 Steve Stricker 69 69 68, Adam Scott (Aus) 69 69 68, Jim Furyk 69 72 65
207 Nick Watney 72 69 66, Keegan Bradley 71 73 63, Matthew Every 71 68 68
208 Chris Kirk 63 70 75, Seung-yul Noh (Kor) 62 71 75, Kevin Stadler 68 71 69, John Merrick 68 72 68, Lee Westwood (Eng) 68 71 69
209 Ted Potter, Jr. 69 68 72, Ernie Els (Rsa) 69 69 71, Tom Gillis 69 69 71, Luke Donald (Eng) 67 72 70, Troy Matteson 72 67 70
210 Pat Perez 69 72 69, Greg Chalmers (Aus) 69 68 73, William McGirt 69 72 69, Jonas Blixt (Swe) 67 72 71, Hunter Mahan 68 72 70, Vijay Singh (Fij) 73 69 68, J.B. Holmes 72 69 69, Dicky Pride 69 72 69, Bo Van Pelt 69 71 70, Johnson Wagner 70 71 69
211 Robert Garrigus 71 67 73, Kyle Stanley 70 70 71, Bill Haas 71 72 68
212 Bud Cauley 68 73 71, Aaron Baddeley (Aus) 68 74 70, Charl Schwartzel (Rsa) 68 65 79, Zach Johnson 70 71 71, Matt Kuchar 70 74 68
213 Jason Day (Aus) 68 73 72, George McNeill 71 70 72, Bob Estes 71 69 73, Sean O'Hair 70 74 69, Marc Leishman (Aus) 72 71 70, Ian Poulter (Eng) 67 71 75, Roberto Castro 72 72 69, John Huh (Kor) 71 73 69, Daniel Summerhays 71 70 72, Josh Teater 71 71 71, Tommy Gainey 72 70 71
214 J J Henry 69 73 72, Geoff Ogilvy (Aus) 72 69 73
215 Scott Piercy 72 70 73, Rickie Fowler 71 72 72
216 Brendon De Jonge 70 73 73, Martin Flores 72 71 73, Jimmy Walker 73 71 72, Brian Harman 71 73 72, Carl Pettersson (Swe) 71 70 75, Blake Adams 69 73 74, Harris English 70 73 73
217 Kevin Na 69 75 73, Scott Stallings 70 73 74, Jonathan Byrd 72 72 73
218 Sang-moon Bae (Kor) 69 72 77, Mark Wilson 74 70 74
219 Graeme McDowell (NIrl) 74 70 75, Padraig Harrington (Irl) 70 74 75
