Washington - Americans Justin Thomas and Jason Kokrak each matched Medinah's course record of seven-under par 65 Thursday to share the lead after the opening round of the US PGA BMW Championship.
Both co-leaders complained of poor warmups for the opening round, then went out and ripped the rain-softened layout in suburban Chicago, while 15-time major winner Tiger Woods struggled to a 71, six strokes adrift.
Thomas, the 2017 PGA Championship winner, made a bogey-free tour to equal the course mark shared by Woods, Skip Kendall and Canada's Mike Weir.
"I had probably the worst warmup I've ever had in my life this morning," Thomas said. "Fairways being this soft definitely played to my advantage."
Kokrak, seeking his first PGA title, fired six birdies and an eagle against a lone bogey.
"Happy to be where I'm at," he said.
Woods, the 15-time major champion fighting for a chance to defend his title at next week's season-ending Tour Championship, shared 50th after 18 holes on a course where he won the 1999 and 2006 PGA Championships.
"I made quite a few mistakes around the greens. Didn't chip it (well). Didn't make putts," the reigning Masters champion said. "It's just not sharp. I just need reps and I haven't had a lot of reps."
Woods withdrew from last week's event at Liberty National with a strained oblique.
"I didn't feel any tightness in my oblique at all," Woods said. "That's a positive."
Woods needs to move into the season points top 30 to qualify to defend his crown next week in Atlanta. He's projected to have to finish 13th or better to pull it off.
"I just need to clean up my rounds and get going," Woods said. "Three- to 5-under par would have been a good score considering how well I hit it."
Five Americans shared second on 66, including 49-year-old Jim Furyk, Joel Dahmen, Lucas Glover, Brandt Snedeker and Patrick Cantlay.
Australian Adam Scott, Canada's Adam Hadwin and Slovakia's Rory Sabbatini were in a pack on 67.
Thomas fired his best score since the Canadian Open just over two months ago and his best opening round since February in Phoenix.
Accurate approaches allowed Thomas to birdie the par-4 fourth and par-5 fifth and seventh holes from inside six feet and he holed a 10-foot birdie putt to close the front nine.
Thomas ran off three consecutive birdies ending with a spectacular 57-foot birdie putt at the par-4 16th then got up and down from a bunker at 18 for par to seize the lead.
"I drove it pretty well and when I got out of position I was able to get it right back," Thomas said. "That one on 16 is a bonus."
Kokrak sank a 21-foot birdie putt at seven but missed the ninth green with his approach and took a bogey. He answered at 10 with an eagle, chipping in from the rough from 86 feet, then added birdies at 11, 14 and 15 to share the top spot.
Kokrak needs to move past two rivals in points to qualify for next week at East Lake.
"I didn't do any number crunching to see what I needed to do to make it to the top 30," he said. "Looking for the Tour Championship but taking it one day at a time - 54 holes to go.
"Playing solid and doing what I've done all season will get the job done."
Top-ranked Brooks Koepka opened on 68 while fellow four-time major winner Rory McIlroy started with a 69.
"I tried to stay as patient as I could," Koepka said. "I didn't play the par-5s well. Every day I'm playing a little better. Hopefully that continues and I'm ready for next week."
Leading scores after Thursday's first round of the US PGA BMW Championship at Medinah in suburban Chicago: (par 72, USA unless noted):
65 - Justin Thomas, Jason Kokrak
66 - Jim Furyk, Joel Dahmen, Lucas Glover, Brandt Snedeker, Patrick Cantlay
67 - Rory Sabbatini (SVK), Scott Piercy, Tony Finau, Adam Scott (AUS), Xander Schauffele, Collin Morikawa, Adam Hadwin (CAN), Rickie Fowler, Chez Reavie
68 - JT Poston, Kevin Kisner, Abraham Ancer (MEX), Brooks Koepka, Patrick Reed, Ryan Palmer, Justin Rose (ENG), Jon Rahm (ESP)
69 - JB Holmes, Corey Conners (CAN), Rory McIlroy (NIR), Graeme McDowell (NIR), Wyndham Clark, Kevin Tway, Kang Sung (KOR), Hideki Matsuyama (JPN), Troy Merritt, Keegan Bradley, Rafa Cabrera Bello (ESP)