Justin Rose leads by four strokes after the third round of the BMW Championship, staying on course to reach the Tour Championship in Atlanta.
The Englishman, who carded a two-under par 69, arrived at Cog Hill ranked 34 in the FedExCup standings. The top 30 will qualify for Atlanta.
Rose produced some daring shots to finish the round at 13-under par.
Australian John Senden was outright second at nine-under after recovering from a bad start to his third round.
Rose started the round tied for the lead with American Mark Wilson but, after back-to-back birdies at the fourth and fifth, had the lead to himself for the rest of the day.
His only miscue was a bogey at the 12th but he recovered with a birdie at 13 then held steady while his challengers failed to keep their composure.
Rose has vowed to learn from his previous experiences while leading on the final day of events, on the last day of this tournament.
Discussing how he will approach it, Rose said: "Just keep seeing good shots and keep playing one shot at a time. I don't think you can get defensive. A four-shot lead isn't really a big enough lead to waste holes."
Wilson's day went wrong with back-to-back bogeys at 12 and 13 followed by a double-bogey at 16. He finished with a 77 to be tied for seventh with Luke Donald, Sergio Garcia, Jim Furyk and Brandt Jobe.
Senden bogeyed three of his first five holes but picked up four shots on the back nine for a 70. Lurking a further shot back is another Australian, Geoff Ogilvy.