Henrik Stenson made three early birdies to seize control at the Tour Championship on Friday.
Stenson quickly expanded his one-shot lead at East Lake with three birdies on the opening four holes and stretched his lead to four shots over Scott with a 4-under 66.
Scott recovered from a rugged start for a 69, while 20-year-old Jordan Spieth had a 67 and was five shots behind.
Stenson and Scott only have to win the Tour Championship to capture the FedEx Cup and the $10 million prize.
Scott also can make a strong case for PGA Tour player of the year if he were to win.
Tiger Woods played his last five holes in 6-over par for a 71 and was 14 shots out of the lead.