First round leaderboard:
-4 G Ogilvy (Aus), L Donald (Eng), P Casey (Eng) -3 J Furyk (US) -2 KJ Choi (S Kor) Selected others: -1 P Mickelson (US), H Mahan (US) +2 M Kuchar (US) +3 D Johnson (US) +4 Z Johnson (US), J Rose (Eng), S Stricker (US) +5 J Overton (US), B Watson (US), M Laird (Sco)
Donald lies seventh in the FedEx Cup points table
English pair Luke Donald and Paul Casey shared a one-shot lead with Australian Geoff Ogilvy after the first round of the Tour Championship in Atlanta.
Donald, one of Europe's wildcards for next week's Ryder Cup, and Casey, who missed out on a pick, fired four-under-par 66s to lead from Jim Furyk.
US Ryder star Phil Mickelson, bidding to supplant an absent Tiger Woods as world number one, was one under.
A $1.35m (£868,000) prize awaits the winner of this FedEx Cup finale.
The overall winner of the FedEx Cup series, which has featured three previous play-off rounds, will earn $10m (£6.4m).
In the last of those - the BMW Championship in Illinois - defending champion Woods failed to qualify for the elite 30-man field for this week's finale at East Lake Golf Club in Georgia.
Mickelson, needing a top-two finish to knock Woods off his perch, holed a 115-yard pitch for a two at the par-four 12th and then sank a 14-foot putt three holes later for his second eagle of the day.
"It was a challenging test," said Mickelson. "There were some good scores and some high ones.
"I was able to shoot one kind of in the middle there with one-under par, and I'll gladly take it."
Matt Kuchar leads the FedEx standings from fellow American Ryder Cup team-mate Dustin Johnson in second.
Kuchar bolstered his bid to land the title when he eagled the par-five 15 to illuminate his otherwise unexceptional round of 72, while Dustin Johnson was another stroke back.
They could be overtaken by in-form Englishman Casey, currently fifth in the table, who is guaranteed the mammoth overall first prize if he tops the final leaderboard on Sunday.
Runner-up in Chicago two weeks ago, Casey was once again a model of consistency, making five birdies and just one bogey - when he found the water on the short sixth.
"I'm very happy with that," reflected Casey. "This is a course which if you play a couple under par every day you are going to put yourself in a wonderful position."
Donald, seventh in the table, needs to win and hope that Kuchar and Dustin Johnson are not second to him.
Casey missed out on a European Ryder Cup wildcard
"It's early days," said 32-year-old Donald, whose form will please Europe captain Colin Montgomerie even if Casey's may be causing the Scot some regret.
"Anything can happen - but it's nice to position yourself.
"The course is firm and fast and that makes it play difficult, but if I could do the same the next three days I would take it right now."
Of the other competing members of American captain Corey Pavin's US team for Celtic Manor, Furyk was most impressive, sinking three birdies in his bogey-free 67 on a day of unspectacular scores.
Hunter Mahan (69) also fared well but Zach Johnson (74), Steve Stricker (74), who is fourth in the FedEx standings, Bubba Watson (75) and Jeff Overton (75) all struggled ahead of the showdown at Celtic Manor which begins on 1 October.
Scotland's Martin Laird was tied for joint last place with Overton and Watson, while England's Justin Rose was just a shot better.
Apart from Donald, the only other member of the European team in action this week is Padraig Harrington, plus vice-captain Paul McGinley, who are competing at the
Vivendi Cup in Paris.
Sweden's Peter Hanson was set to take part but pulled out with a chest infection.