ATLANTA — With two swings, Justin Thomas showed that every shot counts in the FedEx Cup, even at the season-ending Tour Championship.

Thomas had six players ahead of him Friday when he smashed a 335-yard drive down the bottom of the hill on the par-5 18th hole at East Lake, and then a 5-iron that settled 6 feet below the cup for a closing eagle.

Just like that, Thomas had a 4-under 66 and a share of the lead with Paul Casey and Webb Simpson and was back in control — a loose term the way this tournament is shaping up going into the week — of his chase for the $10 million bonus.

"It's nice to have everything in my own hands and know that if I just take care of what I need to do, then it's over," Thomas said.

It's not over yet, not even close.

Casey stumbled with some errant tee shots into the troublesome rough for back-to-back bogeys in a 67 that slowed his momentum. Simpson paid for a wild drive on No. 13 with a double bogey and made nothing pars coming in for a 67.

They joined Thomas at 7-under 133.

Adam Hadwin of Abbotsford, B.C., is five shots back and tied for 18th after a 67.

As one of the top five seeds, Thomas only has to win the Tour Championship to capture the FedEx Cup. Even a third-place finish might be enough to take home golf's richest bonus depending on who wins.

But that list is plenty deep after two sweltering days at East Lake.

Jon Rahm, the No. 5 seed who also has a clear path to the top prize, played bogey-free for a 67. He was one shot behind, along with Patrick Reed (65), Justin Rose (66) and Gary Woodland (67), all of them trying to win for the first time this year.

Dustin Johnson, the No. 3 seed, has been sputtering along. He failed to birdie either of the two par 5s, managed only a 69 and still was only four shots behind.

"I just want to get within striking distance," Johnson said. "If I can get it within three, I would be happy."

He was four behind, so it doesn't require much math to figure out he's not far away.

Jordan Spieth was lucky to still be just four shots behind. The No. 1 seed in the FedEx Cup missed five straight greens in regulation on the back nine and kept in the game with some crucial par putts. He had to settle for a 70 and headed straight for the practice area.

Twenty players from the 30-man field were under par, meaning they were separated by just six shots with 36 holes ahead of them.

"It's the easiest one to win because there's only 30 guys," said Kevin Kisner, who shot another 68 and was three behind. "But then I look up there and everyone is 6 under, and it doesn't look so easy."

Thomas made birdies with a wedge in his hand, failed to save par from a bunker on the fifth hole, and then turned a mediocre round into a solid one with that 5-iron into the 18th for birdie.

He already can state his case as the best player on the PGA Tour this year, with five victories and his first major at the PGA Championship. Thomas outlasted Spieth and Marc Leishman to win at the TPC Boston three weeks ago, and now he's tied for the lead going into the weekend at East Lake.

Much like Spieth in 2015 when he ended his best season with the FedEx Cup, Thomas would love to have the perfect ending.

"I want to win any week," he said, "but it definitely would be a nice cap."

Casey and Simpson are enduring long droughts. Casey last won at the KLM Open in 2014, while Simpson last won four years ago in Las Vegas. Both overcame a few stumbles on the back nine to share the lead.

Casey seems to have done everything but win the last three years, with six top-5 finishes in the last eight FedEx Cup playoff events.

"It would cap off a very good season, make a very good season a great season," he said. "Yeah, it would be a lot of satisfaction in that. Hopefully, ask me again on Sunday and I can give you the full explanation. Right now, I'm too busy just trying to focus on trying to string together four great rounds of golf. It's amazing how this golf course just bunches and you can't seem to get away.

"Guys are right there, sort of biting at your heels," he said. "So it's going to be a tough one."