Russell Henley shot 61 to move into a two-stroke lead after the first round of the Tour Championship, finishing with three straight birdies to move to nine under par.
It leaves him two clear of defending champion Scottie Scheffler, the world number one finishing on his own in second place at the East Lake Golf Club.
Rory McIlroy was the best of the Irish on four under par, with Shane Lowry finishing on even par. McIlroy made it to the turn on three under, after a spectacular 30-foot putt for eagle at seven.
The back nine was more mixed as the county Down man mixed three birdies with two bogeys.
For Lowry, it was a more consistent day, with two birdies and two bogeys to finish on level par.
The course was set up to be more challenging with pins tucked in corners of the greens but it mattered little. In total, 22 of the 30 players were under par, six players were even and just two players were over par. The combined score of the field was 82 under par.
Perhaps it was the heavy rain that pummelled the Atlanta area Tuesday and Wednesday that helped the golfers, with Round 1 played under preferred lies rules due to evening downpours. This allowed balls on the fairways or other closely mown areas to be lifted, cleaned and placed in a preferred spot.
The Tour Championship winner will also be crowned FedEx champion and will pocket the $10m on offer, which equates to roughly €8.6m.
Additional reporting: Reuters
