ATLANTA -- FedEx Cup standings leader Justin Thomas squandered his pre-tournament lead but birdied the 18th hole on Thursday, Aug. 22, to maintain a share of the lead with two others through one round at the Tour Championship in Atlanta.

Thomas shot even-par 70 at East Lake Golf Club and was joined atop the leaderboard by Xander Schauffele, who shot the low round of the day with a 64, and Brooks Koepka (67), who also birdied 18.

The new staggered-start scoring system -- in which players were given advantages based on their standing through the BMW Championship -- had Thomas starting at 10 under, two strokes ahead of second-place Patrick Cantlay. Koepka began in third at 7 under, while Schauffele began at 4 under, tied with four others for sixth.

Northern Ireland's Rory McIlroy, who was critical of the scoring system on Wednesday, started in fifth at 5 under and shot 66 to hold fourth place alone at 9 under.

Another stroke back at 8 under are Cantlay (who shot even-par 70) and Matt Kuchar (66), with Japan's Hideki Matsuyama (66) alone at 7 under.

Thomas had an up-and-down day. After two birdies and a bogey on the front nine, he dropped back to even with a bogey at the 12th. A birdie at 14 got Thomas back into red figures, but only temporarily, as he double-bogeyed the par-3 15th after his tee shot found the water.

Thomas, who won the BMW Championship last week, bounced back by reaching the par-5 18th fringe in two and two-putting for birdie.

Schauffele, who beat out Thomas to win the Tour Championship in 2017, closed the six strokes between him and Thomas with three birdies on each side of the card in a bogey-free round. No other player in the field shot lower than 66.

"I figured once the cameras started following us, I was shooting a good score," Schauffele told "That was my giveaway."

Koepka, the world's top-ranked player, erased back-to-back birdies at Nos. 4 and 5 with consecutive bogeys at Nos. 9 and 10. He finished strong, however, making birdie putts inside five feet at the 15th and 16th before draining a 12-footer at the 18th to share the lead.

McIlroy, the 2016 winner and third-ranked player in the world, also finished with a flourish. He made birdies at Nos. 13, 15, and 17 after sandwiching two birdies around his lone bogey at No. 5.

World No. 2 Dustin Johnson, who started the day at 3 under, shot 73 to settle at even par, tied for 23rd.