Jim Furyk, co-leader overnight with Brandt Snedeker, withstood strong runs from Tiger Woods and Steve Stricker to move one stroke in front after Saturday's third round of the BMW Championship.
Fresh from his stunning 12-under-par 59 on Friday, American Furyk recorded three birdies after the turn before bogeying the last for a two-under 69 on a sunny day at Conway Farms Golf Club where the breezes strengthened in the afternoon.
Graeme McDowell shot a 72 to go to two over, while Rory McIlory recorded a three-under 68 to move up to third from last.
In pursuit of his first victory since the 2010 Tour Championship, Furyk played mainly rock-steady golf to post a 13-under total of 200 in the third of the PGA Tour's four lucrative FedExCup playoff events.
The 43-year-old lipped out with a long-range birdie attempt on the 18th green that would have put him three ahead of the chasing pack, then missed a par putt from five feet to card his second bogey of the day.
Stricker, who holed out with a sand wedge from the fairway to eagle the par-four 15th, was alone in second after shooting a 64, ahead of fellow Americans Snedeker (71), at 11 under, and Zach Johnson (69), at 10 under.
"I had a nice little run to at least get myself in there where I have a chance tomorrow" - Tiger Woods
World number one Woods was a further shot back in fifth, having briefly got to within two of the lead with a storming run of six birdies in seven holes around the turn on the way to a 66.
Woods' momentum stalled when he bogeyed the driveable 15th after dumping his tee shot into water but he birdied the last to end his round four strokes off the lead.
"I was caught between three-wood and five-wood and tried to hit a little soft cut three-wood and just hit a pull-straight ball right in the water," Woods, seeking his sixth PGA Tour victory of the year, told reporters about his tee shot on 15.
"But I had a nice little run to at least get myself in there where I have a chance tomorrow. I made a big bomb there at six, which was nice, and then I got hot from there."
Woods, who was livid after being docked two strokes for a rules violation on his opening hole in Friday's second round, launched his sizzling birdie run by draining a 30-footer at the par-three sixth.
Seventy players have qualified for the elite BMW Championship, the PGA Tour's penultimate playoff event, and any improvement in the overall FedExCup points standings after Sunday's final round could be crucial.
Of the 30 who advance to next week's season-ending Tour Championship, any of the top five would automatically clinch FedExCup honours and a staggering $10 million bonus with victory in Atlanta.