Luke Donald is two shots off the lead after shooting a four-under-par 66 in the first round of the Tour Championship in Atalanta.
American Bradley Keegan, the US PGA champion, leads after hitting four birdies in the last seven holes.
Justin Rose birdied the 17th as he ended his round one under with a 69.
Donald and his compatriot Rose are among five players with a realistic chance of clinching the FedEx Cup in the concluding event of the series.
Americans Webb Simpson and Dustin Johnson lead the standings but all 30 players have a theoretical chance of overall victory.
Matt Kuchar is fifth and a win for any of the top five would secure the Cup, and a $10m (£6.4m) bonus.
But any of the elite field, which has been whittled down from 125 in the first of the four FedEx events, can still win overall should the top five fall short.
Jason Dufner, who lost a play-off to Keegan in last month's US PGA, made the brightest start, with birdies in three of the first four holes on his way to a 66.
Donald and Rose were interrupted by a thunderstorm that suspended play before completing their rounds in torrential rain.
England's Rose is third in the FedEx rankings after last week's BMW win in Chicago, while world number one Donald is fourth.
Johnson won the opening event, the Barclays, in New Jersey at the end of August before Simpson won the 100-strong Deutsche Bank tournament in a play-off in Boston at the beginning of September.
Donald is also second on the PGA Tour money list for 2011 and top of the European Tour equivalent, the Race to Dubai, and is bidding to become the first player to win both lists in the same season.
HOW THE FEDEX CUP WORKS
Players pick up points throughout the regular season in each event they play. Most tournaments give 500 points to the winner
The top 125 players enter the play-offs, which consist of four tournaments and where winning carries 2500 points
The field is whittled down to 30 for the final event, the Tour Championship
Points are reset, so that the number one player has 2500 points, number two has 2250 and number 30 has 210
In theory, all 30 players can win the FedEx Cup, but only the top five are guaranteed the trophy if they win the Tour Championship
FEDEX CUP STANDINGS
1. Webb Simpson (USA) 2,500pts
2. Dustin Johnson (USA) 2,250
3. Justin Rose (Eng) 2,000
4. Luke Donald (Eng) 1,800
5. Matt Kuchar (USA) 1,600
