Justin Thomas insisted he will be "fine" after losing his FedEx Cup cushion in round one of the season-ending Tour Championship.
BMW Championship winner Thomas had a two-stroke advantage after the format change for the Tour Championship at East Lake this week.
Instead of a points reset for the Tour Championship, players started on different scores – with Thomas top of the leaderboard at 10 under prior to round one.
However, Thomas ended Thursday's round tied for the one-shot lead alongside Xander Schauffele (64) and Brooks Koepka (67).
Thomas – the 2017 FedEx Cup champion – posted an even-par 70 and he said: "I'm fine. I'm tied for the lead.
"I played better than I scored today. I still can't believe those two short putts. I hit them where I wanted to.
"I feel like I played a lot of good golf through those last five holes. I'll be fine."
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.
"It was frustrating obviously because they were so close," the American star said. "To drive it as bad or hit as few fairways as I did through 13 holes and miss a couple of putts, to come in to the house at 10 under feels pretty good."
While Thomas made a slow start, countryman Schauffele catapulted himself up the leaderboard thanks to the best round of the day.
Schauffele, who was six shots adrift when he teed off, carded a six-under-par 64 to move into a three-way tie for the lead.
Winner of the 2017 Tour Championship as he was named PGA Tour Rookie of the Year, Schauffele said: "It was a good day. I told myself I'd keep my head down all of Thursday. The plan is to keep it down [Friday] and most of Saturday. It seemed to work today."
Koepka was third in the standings and three strokes behind Thomas before the FedEx Cup decider got underway on Thursday.
The four-time major champion had five birdies and two bogeys in a relatively steady opening to his campaign.
"It's nice to be tied for the last after the first day,'' he said. "I'm not very good at getting off to good starts, so I usually never get in that position. But it's nice. Three more days to grind it out and finish the year strong.''