The BMW Championship first-round leaderboard
-7 J Thomas, J Kokrak (both US); -6 J Furyk, J Dahmen, L Glover, B Snedeker, P Cantlay (all US); -5 R Sabbatini (Svk), S Piercy, T Finau, X Schauffele, C Morikawa, R Fowler, C Reavie (all US), A Scott (Aus), A Hadwin (Can)
Selected others: -4 J Rose (Eng), B Koepka, P Reed (both US); -3 R McIlroy, G McDowell (both NI), -2 P Casey, T Fleetwood, I Poulter (all Eng); -1 T Woods (US)
Justin Thomas says he had the worst warm-up of his life before tying the course record at Medinah to share the BMW Championship lead after round one.
Americans Thomas, 26, and Jason Kokrak, 34, both hit a record-equalling seven-under par 65 in Illinois on Thursday.
Despite carding a round of seven birdies and no bogeys, Thomas said he "couldn't hit the ball" in practice before teeing off.
"I had the worst warm-up I've ever had in my life," he said.
"I had no idea what I was doing. I didn't know how I was going to hit it.
"I've had that happen plenty of times, just not quite that extreme. I'm usually pretty good at finding my way around a golf course and finding something, but definitely didn't expect that."
The BMW Championship is the second of three events in the US PGA tour's FedEx Cup play-offs. The top 30 players in the rankings after this tournament will qualify for the Tour Championship on 22 August for the chance to become FedEx Cup champion.
Thomas, who won the 2017 FedEx Cup, has moved into projected first place in the rankings after his opening round.
He is without a victory this year, having been hampered by a wrist injury that caused him to miss the US PGA Championship, which he won in 2017.
The other golfers to hit 65 at Medinah all did so during a US PGA Championship - Skip Kendall in 1999, Mike Weir in 2006 and Tiger Woods in winning the title, also in 2006.
"It's been an odd season just because I've missed three tournaments, but the difference with this season and any other season is I'd won," said Thomas.
"I'm playing every bit as good as I have any other year this year, for sure."
Americans Patrick Cantlay, Jim Furyk, Joel Dahmen, Lucas Glover and Brandt Snedeker are tied for third, one shot off the lead.
Defending FedEx Cup champion Justin Rose bogeyed the last to finish on a four-under 68, level with world number one Brooks Koepka, who started the tournament in first place, and Patrick Reed, who won The Northern Trust last week.
Northern Ireland's Rory McIlroy, who started the week third in the FedEx Cup standings, is a shot further back on three under alongside compatriot Graeme McDowell.
Englishmen Tommy Fleetwood, Ian Poulter and Paul Casey sit at two under - one better than 15-time major champion Woods, whose 71 leaves him projected 47th in the rankings and needing three strong rounds to reach the Tour Championship, which he won last year.