WASHINGTON (AFP) — World No. 1 Scottie Scheffler, the reigning Masters champion, birdied the last three holes to grab a five-stroke lead after Thursday's first round of the US PGA's season-ending Tour Championship.

The 26-year-old American began the day at 10-under par with a two-shot edge under a staggered start scoring system based on season points.

Scheffler stretched his advantage by firing a five-under par 65 at East Lake in Atlanta, sparked by birdie putts of just over 14 feet at the 16th, 11 feet at 17, and a tap-in at the par-5 18th after driving the green in two.

"I felt like I played good all day and I was only two under so to get those last three birdies at the end was definitely some icing on the cake," Scheffler said.

"I played pretty solid. That's always a good way to finish off the round."

Scheffler, who hadn't won a PGA title when the year began, won four in two months capped by his first major title at Augusta National, and could cap an incredible season by taking the $18 million FedEx Cup playoff crown.

Xander Schauffele, the Tokyo Olympic winner, was second on 10-under after shooting 66. Schauffele began his round on 6-under, four back of Schauffele.

"It's easy to get ahead of yourself," Schauffele said. "It's a stressful place to play if you're not on top of your game. I'm just trying to piece some things together for Sunday."

US Open winner Matthew Fitzpatrick of England was third on 9-under after matching Chile's Joaquin Niemann for the day's low round with a 64. The British star closed with an eagle putt from just inside 13 feet to a bogey-free day six shots adrift.

"Bogey-free rounds are pretty much my favorite," Fitzpatrick said. "A great day. Definitely felt comfortable out there."

Defending champion Patrick Cantlay, who began on 8-under only two behind Scheffler, managed a 70 thanks to a 22-foot eagle putt at 18 to share fourth overall on 8-under with Niemann.

The top 30 players in season points qualified for the final playoff showdown, Scheffler starting with an edge on the field thanks to his top performance all season.

"For me, just approaching this as a four-day event and not really looking at the strokes," Scheffler said. "I'm looking at who is in the lead. Just going out there and plodding along is going to be best for me. I don't think looking at the lead is going to help."

"Five-shot lead, but it's only round one. There's still a lot of golf left to play."

Scheffler sank a 12-foot birdie putt at the third hole then drove the green in two at the par-5 sixth and made an eagle putt from just outside 16 feet. He missed the green at the par-3 ninth and made a bogey, but at the turn still led the field by five.

McIlroy's wild round

Four-time major winner Rory McIlroy shared sixth at 6-under with Australian Cameron Smith, the reigning British Open champion, and South Korean Im Sung-jae after all three fired 67s.

"Tomorrow is a pretty pivotal day for the rest of the field just to try to get a little closer to where Scottie is," McIlroy said.

McIlroy opened with a triple bogey, went bogey-birdie at the second and third as well as the fourth and fifth holes, then eagled the par-5 sixth from 35 feet in the rough and finished the front nine birdie-bogey.

The Northern Ireland star birdied 12 but took a bogey at 13 after sending his tee shot way left only to close with birdies on four of the last five holes, the most sensational of the lot on a 35-foot putt at the par-3 15th.

"The last few holes there were huge," McIlroy said. "I felt like I played myself out of the tournament the first few holes, and I played myself back into the tournament the last few holes."