Potomac - Sweden's David Lingmerth birdied four of his first six holes on the way to firing a five-under par 65 and grabbing a one-stroke lead after Thursday's opening round of the PGA National.
The 29-year-old Swede, whose uncle played for the 1987 NFL Cleveland Browns, seeks his second PGA title after winning the 2015 Memorial, downing England's Justin Rose in a playoff.
Lingmerth, third at the 2015 National, was one shot in front of a pack on 66 that included Australia's Marc Leishman, South Korean Kang Sung, Canada's Nick Taylor and Americans Troy Merritt, Daniel Summerhays and Johnson Wagner.
"I know I can probably contend here and play well," Lingmerth said. "Feeling great. Had a solid first day, so now it's just a matter of keeping it going."
The par-70 TPC Potomac layout, hosting its first PGA event since 2006, was formidable, with Players Championship winner Kim Si Woo of South Korea shooting 79 a day after his 22nd birthday and defending champion Billy Hurley on 73.
Justin Thomas, the 12th-ranked American who played in Sunday's final group two weeks ago at the US Open, made a quadruple bogey 9 at the 10th hole - his career-high score on any hole - and stumbled to a 74.
But Lingmerth had already mastered the course before, winning a Web.com Tour event at the former Avenel layout in 2012.
"It sets up well for me. Any time you come back to a golf course where you've won, you have great memories from the get go," Lingmerth said.
Lingmerth, who began on the back nine, sank a 12-foot birdie putt at the par-5 10th but stumbled with a bogey at 11 after finding a greenside bunker with his approach.
He responded with three birdies in a row starting at the par-4 13th, his longest putt an 18-footer at 15, and added back-to-back birdies at 18 and 1, the latter on a 24-foot putt. He followed with a 20-foot birdie putt at the fourth but closed with a bogey to halve his lead.
"Got a nice start. Hit a lot of fairways," said Lingmerth, who let the field by hitting 12 of 14 fairways.
"Putted quite well. Those are two main things, hit a lot of fairways and give yourself some chances."
Summerhays, another back-nine starter, sank a stunning 45-foot birdie putt at the par-3 12th then eagled the par-4 13th with an even-more incredible 105-yard hole out from the fairway and followed with a 10-foot birdie putt at 14.
He made eight-foot birdie putts at the first and fourth holes took a bogey at the par-4 sixth and three-putted for double bogey at the par-4 eighth to fall back before a closing birdie.
Leishman, who also began off the 10th tee, made three birdies in a row starting with a 13-foot putt at the 13th and closed the run by rolling home a 60-foot bump and run shot from off the front of the 15th green.
"It was nice to reward myself with making that chip shot," Leishman said. "It's just a really nice to start a tournament in that way."
Taylor began on the back nine and birdied five of his first six holes, but stumbled back with a double bogey at the par-3 17th.
After birdies from within five feet at 10 and 11, Taylor sank a 20-foot birdie putt at the par-3 12th, parred 13, then holed short birdie putts at 14 and 15.
"It was a great start," Taylor said. "I was hitting fairways, able to get it close from there. Just hitting it close and making all the putts, too."
Kang had five birdies and two bogeys in his first 10 holes before closing with seven pars and a six-foot birdie putt at 14.
Scores after Thursday's opening round of the US PGA National (par-70, USA unless noted):
65 - David Lingmerth (SWE)
66 - Troy Merritt, Marc Leishman (AUS), Johnson Wagner, Kang Sung (KOR), Nick Taylor (CAN), Daniel Summerhays
67 - Russell Henley, Zac Blair, Martin Laird (SCO), Geoff Ogilvy (AUS), Patrick Reed, James Hahn, Bryson DeChambeau
68 - Martin Flores, Ricky Barnes, Lucas Glover, Sam Saunders, Curtis Luck, Grayson Murray, Matt Jones (AUS), Mackenzie Hughes (CAN), Ben Martin, Kevin Streelman, Arjun Atwal (IND)
69 - Jason Gore, Bud Cauley, Tony Finau, D.A. Points, Michael Kim, Bill Haas