Keegan Bradley birdied six of the first nine holes on his way to firing a seven-under par 64 to grab the lead after Thursday's first round of the BMW Championship.
The 36-year-old American matched his low US PGA Tour nine-hole score with a 29 from the 2013 Byron Nelson and finished 18 holes at Wilmington (Delaware) Country Club one stroke ahead of Australian Adam Scott.
"This is a good start. I'm proud of the way I played," Bradley said.
"If you hit the ball in the fairway, there are a lot of opportunities. I did that a lot today and the ones I missed I was able to manage."
Ireland's Shane Lowry shared third on 66 with PGA Championship winner Justin Thomas and fellow American Harold Varner with a pack on 67 including two-time major winner Collin Morikawa and Tokyo Olympic champion Xander Schauffele.
The event is the second of three FedEx Cup playoff tournaments with the top 30 on season points after Sunday advancing to next week's season-ending Tour Championship in Atlanta.
Bradley and Scott are both in position to jump into the top 30 from 44th and 45th in points respectively.
Bradley, the 2011 PGA Championship winner seeking his first PGA triumph since the 2018 BMW Championship, sank a 13-foot birdie putt on the first hole.
He added birdies at the third and fourth, sank a 30-foot birdie putt at the sixth, dropped his approach to three feet and holed the birdie putt at the par-3 seventh, saved par with an eight-foot putt at the eighth and made a birdie putt from just inside 40 feet at the ninth.
"I made a nice putt on the first hole and just kept it going," said Bradley. "It was really a fun day."
Bradley answered a bogey at 11 with birdies at 14 and 15 to complete his day atop the leaderboard and just ahead of playing partner Scott, the 2013 Masters champion who birdied three of the first six holes and three of the last five.
"There was a lot of good solid stuff. I'm very pleased," Scott said.
"I watched Keegan and I was really just trying to follow his lead. He kind of had everything going the way he wanted... I was drafting off him."
Four-time major winner Rory McIlroy shared 13th on 68 despite a triple-bogey disaster at the par-3 15th, where he found water off the tee and missed a double bogey putt from 3 1/2 feet.
"Just that one tee shot on 15," McIlroy said. "I felt like I had probably half a club too much so I was trying to hit like a cut in there over the water and I just double-crossed it -- and then compounded that by the three-putt.
"But overall the rest of it was pretty good."
Masters champion and world number one Scottie Scheffler was also on 68 while season points leader and fellow American Will Zalatoris, runner-up at the US Open and PGA Championship, shared 34th on 70.