Marc Leishman will take a five-stroke lead into the final round of the BMW Championship after producing a superb 68 but it was another disappointing day for Rory McIlroy.
Leishman, who sat seventh in the FedEx Cup rankings before the tournament began, mixed five birdies with two bogeys in his third round to move to 19 under par.
Fellow Australian Jason Day and American Rickie Fowler were Leishman's nearest challengers on 14 under par, with Englishman Justin Rose a further two strokes back in fourth.
Beginning the day three shots clear of the chasing pack, Leishman rolled in his 14-foot birdie putt at the third but gave a shot back at the next.
Another birdie from 20 feet at the fifth took the 33-year-old back to 17 under but he dropped a shot at the seventh to return to where he started the day.
Leishman then made gains at the eighth, 13th and 18th to extend his advantage to five shots.
After his round, Leishman told Sky Sports Golf: "I'm feeling good. The game's in a really good spot but the way the course is getting, you've got to be right on your game. It's very easy to have bogeys out there.
"Hopefully the putter stays hot like it has been and when I give myself some chances I can make them."
For McIlroy his hopes of making the Fedex Cup are now over. He came into the tournament needing to climb 19 places in the play-off standings but lost further ground in the third round.
The Northern Irishman did manage to hit five birdies but added them to two bogeys and a double bogey on the 14th for a round of 70 that leaves him tied for 52nd and 17 shots off the lead.
