|Tour Championship final-round scores (US unless stated)|
|-11 Billy Horschel -8 Jim Furyk, Rory McIlroy (NI) -7 Justin Rose (Eng), Chris Kirk, Jason Day (Aus) -6 Ryan Palmer -5 Rickie Fowler|
Rory McIlroy missed out on a £6m bonus as Billy Horschel clinched the Tour Championship and with it the overall FedEx Cup title and the bumper payout.
McIlroy, 25, went into the final round of the Tour climax as overnight co-leader with Horschel but finished three adrift of the American in Atlanta.
The world number one ended eight under after a 71, which included a double bogey and three other dropped shots.
Fellow American Jim Furyk was also tied second, with Justin Rose tied fourth.
McIlroy was one of five players - along with Horschel, Chris Kirk, Bubba Watson and Hunter Mahan, who could seal the FedEx Cup title and bonus with outright victory in Atlanta, though in theory any of the elite 29-man field could have triumphed.
Northern Ireland's McIlroy made a double bogey via the water on the sixth before three consecutive bogeys from the ninth, although he finished his round with three successive birdies and a par in his last event before the Ryder Cup.
"It was a week too far," said the 25-year-old, who was competing in his eighth tournament in 10 weeks. "I was making mistakes that I don't normally make. But Billy deserved it. He played the best golf."
The points-based FedEx Cup concludes with four play-off tournaments which take place after the regular 41-event PGA Tour season. Only the top 125 players, who accumulated the most points during the season, were eligible for the opening play-off event - The Barclays.
That number was whittled down to the top 30 by the time of the finale at East Lake in Atlanta, though Dustin Johnson's time out from golf reduced the field to 29.
Horschel fired his 12th consecutive round in the 60s to take the title, a first prize of £880,000 and the overall bonus of £6.2m.
The 27-year-old graduate from the University of Florida was only 60th in the standings prior to the opening play-off tournaments, but finished runner-up in the second event, the Deutsche Bank Championship, before winning the next tournament, the BMW Championship at Denver.
"I'm on cloud nine, it's unbelievable," said Horschel.
"It's just unbelievable, everything that's happened the last two weeks, and especially having a kid on the way. I'm not sure life can be better than this."
American Chris Kirk had led the overall competition going into the Atlanta tournament, but suffered a poor third round when he shot a 71 to drop from tied second to seventh.
He eventually finished the Tour Championship tied for fourth on seven under alongside England's Rose and Australia's Jason Day.