Henrik Stenson continued his impressive start to the Tour Championship as a two-under 68 moved him three shots clear in Atlanta.
The Swede's round at the East Lake Golf Club on Friday saw him edge into nine under, three shots clear of Jordan Spieth (66).
Stenson, the 2013 FedEx Cup winner, is projected to finish top of the season-ending standings once more as results stand.
World number one Jason Day, who started the tournament as the points leader, shot a 71 to be nine shots off the lead.
Stenson carded a 63 in the first round, but his second was trickier as he mixed four birdies with two bogeys.
Spieth's strong opening to the event continued as he went through blemish-free, making two birdies on each of the front and back nines.
The American two-time major winner made two big par saves on the front nine before a 19-foot birdie putt saw him finish with a 66 on a tough day for scoring.
Englishman Paul Casey is outright third at five under despite encountering trouble on the front nine, a bogey on the fifth followed by a double on the sixth.
Zach Johnson (70) sits at four under, a shot ahead of Rory McIlroy (71) and Steven Bowditch (69).
Former world number one McIlroy endured an inconsistent second round, with four bogeys costly for the Northern Irishman.
Justin Rose's 68 sees him in seventh, while Rickie Fowler is at one under – a shot ahead of Day, J.B. Holmes and Brandt Snedeker.
Day has been unable to get going in Atlanta and it continued on Friday as he bogeyed three par-fours.