Sergio Garcia charged into a three-shot lead after the third round of the Tour Championship, shooting a 67 to pull clear of Phil Mickelson and Anthony Kim.
The Spaniard posted an eight under total of 202 with Americans Mickelson (69) and Kim (72) second on five under.
Colombian Camilo Villegas is three under with only seven players under par in the 30-man field.
Garcia, who was beaten 5&4 by Kim in their singles showdown at The Ryder Cup, enjoyed a measure of revenge as he totally outplayed his opponent in benign conditions.
Starting the day two strokes behind, he pulled level with birdies at the seventh and ninth and then eased clear on the back nine.
"I played pretty solidly overall," said Garcia
Kim was out of sorts on Saturday, particularly off the tee, finding just four fairways as he struggled with his accuracy.
He kept himself in the hunt with a great putting display on the front nine, but managed just one birdie all day.
Kim's wayward tee shot on the ninth struck a spectator on the forehead, knocking the man to the ground and leaving a massive gash on his forehead.
The spectator, David Whitfield, was quickly attended to by medics and although he remained conscious, was in considerable pain with, his forehead splattered with blood.
Kim parred the hole but was clearly unsettled.
"I felt terrible," Kim said. "You never want to see that anywhere. He's going to need some stitches but he's going to be all right."
Kim revealed that he had a rushed preparation after mistaking his tee-time.
He thought it was 11:55am, when in fact it was 30 minutes earlier.
"I was a little thrown off, but no excuses," he said.
Mickelson, meanwhile, does not seem to be suffering a Ryder Cup hangover.
"I made some good putts today," said Mickelson.
"Anything after the Ryder Cup is going to be a letdown but this is the last tournament of the year in the US and I'm trying to give it everything I've got.
"One win would change the way I look at the year."
Vijay Singh moved within 18 holes of the FedEx Cup play-off title when he completed another mediocre round.
A 72 was Singh's best score of the week and left him nine over.
Singh only has to complete the final round to be crowned the play-off champion and pick up a £5.4million bonus. He eliminated any suspense by winning the first two play-off events.
"It's difficult to play when you're trying not to hurt yourself," he admitted.
