Jordan Spieth stayed on course for a $10 million payday at the Tour Championships here Saturday, firing a two-under-par 68 to snatch a one-shot lead as Sweden`s Henrik Stenson faltered.
In torrential rain at the East Lake Golf Course, Spieth closed out a solid round in difficult conditions with a superb curling 20-foot birdie putt on the 18th to cap a battling third round performance.
Spieth will pocket a $1.48 million winner`s check as well as a $10 million bonus for clinching the FedEx Cup playoff series if he hangs on to his lead in Sunday`s finale to the USPGA season.
"It was a fantastic day," Spieth said. "I would have taken even par when the day started and so to finish a couple under was fantastic."
But it was a frustrating third round for overnight leader Stenson, who saw his three-shot lead evaporate after a scratchy two-over-par 72 which included four bogeys and only two birdies.
Stenson looked to have overcome a wobble on the back nine, when he posted consecutive birdies on the 10th and 11th before a birdie on the 14th restored his two-shot cushion.
However Spieth notched a birdie on the 15th to halve Stenson`s lead and when the Swede bogeyed the 17th the two rivals headed to the 18th as joint leaders before Spieth produced another birdie to take sole ownership on eight-under 202.
Stenson admitted he had struggled in the grimy conditions which he likened to a muddy endurance race.
"Wet, muddy, rough," Stenson said. "What is that race called, Tough Mudder? Is that what it`s called? That`s what it felt like.
"All in all, it was a tough day and I didn`t play my best, but I still think I kept it together quite nicely in tough conditions."
Stenson, on 203, has a three-shot advantage over his nearest rivals, with Rickie Fowler and England`s Paul Casey tied for third on four under.
Fowler produced a scintillating back nine performance which included four birdies to finish with a three-under-par 67.
"With the conditions, I hit some great shots, made some good putts and it`s going to go a long ways to put myself in good position for Sunday," Fowler said.Northern Ireland`s Rory McIlroy was a further shot back on three under alongside Zach Johnson after carding an even-par 70.
McIlroy made a shaky start with bogeys on the first and fourth holes before he suddenly starting finding his putting range.
He rolled in a 26-foot effort on the seventh for his first birdie and then followed it up with a 21-footer on the ninth to go to the turn at level par.
A fine approach on the 12th left him a two foot tap-in for a third birdie before an 18-foot birdie putt on the 13th took him to two under.
A bogey on the 14th, however, checked his momentum before another birdie on 15 put him within sight of the lead.
A bogey on the 16th followed by a birdie on the 17th summed up his day, and a disastrous double-bogey on the par-three 18th dropped him back to level par for the day.
Elsewhere Saturday world number one Jason Day struggled to mount a challenge to the front-runners, with two bogeys and two birdies leaving him with a par 70, level par after three rounds, eight shots off the lead.