Thomas, Koepka and Schauffele tied for Tour Championship lead
Justin Thomas and Brooks Koepka are in a three-way tie with Xander Schauffele for the Tour Championship lead after the opening round.
The trio ended Thursday level at 10 under in the FedEx Cup decider, despite 2017 winner Schauffele producing the best round of the day via a six-under-par 64.
BMW Championship winner Thomas entered the tournament with a two-stroke advantage after the format change for the season-ending event at East Lake.
Instead of a points reset for the Tour Championship, players started on different scores – with Thomas top of the leaderboard prior to round one.
Schauffele was six shots adrift when play got underway but the American's bogey-free round, which included six birdies, and coupled with Thomas' even-par 70 saw him earn a share of the one-stroke lead.
It was a low-key start from Thomas, who is eyeing his second FedEx Cup title after claiming the trophy in 2017.
Afforded a head start thanks to his BMW Championship triumph, Thomas endured a mediocre opening in Atlanta, where a double-bogey and a pair of bogeys to go with four birdies saw his advantage evaporate.
Four-time major champion Koepka used a three-under-par 67 to catapult himself into a share of the first-round lead on Thursday.
Koepka, who was three shots behind Thomas at the start of the day, had five birdies and two birdies in a relatively steady opening to his campaign.
The American star finished with a flurry, birdieing three of his final four holes to join Schauffele and Thomas atop the standings.
Former world number one Rory McIlroy is a shot off the pace heading into the second round thanks to his 66.
The 2016 FedEx Cup champion only dropped one shot, recording five birdies to be in solo possession of fourth spot, ahead of Matt Kuchar (66) and Patrick Cantlay (70).
It was a difficult day for Dustin Johnson, who struggled to a three-over-par 73 to be even par and tied for 23rd in the 30-man field at the end of the first round.