World number one Scottie Scheffler was part of an eight-man group atop the leaderboard after the first round of the Charles Schwab Challenge, played at Colonial Country Club in Texas.
Scheffler, who shot a bogey-free 66 despite only hitting 50 per cent of the fairways in regulation, was joined by fellow Americans Harold Varner III, Chris Kirk, Beau Hossler, Patrick Reed and Webb Simpson, as well as Canadian Nick Taylor and Australian Cam Davis.
Hossler produced the most notable round, with two eagles – both coming on par-fours – in his last four holes to fly up the leaderboard.
One shot off the lead were a group including Davis Riley and Kevin Na, while pre-tournament favourite Jordan Spieth was back at one under, tied with Victor Hovland and Max Homa.
Spieth, who is from Texas, has an impeccable record at Colonial, with seven top-10 finishes – including three runners-up and a win – from nine starts on the PGA Tour.
Speaking to the media after finishing his round, Spieth said he is battling his putter at the moment but that he is confident things will turn in his favour.
"I think I'm typically more comfortable with reads here, although today here was totally different, I misread a number of putts today," he said.
"But I stroked it beautifully, I just felt great about the way I putted, I just didn't get much to go.
"Those are the kind of rounds where you can either look at it negatively, or you can say at it like 'hey, that lid is going to come off one of these times, and all of a sudden they're all going to pour in'.
"It's done that for me [previously] at Colonial, so I think that's the attitude I'm going to take."
At even par were a strong international group including Chile's US PGA Championship main character Mito Pereira, Colombia's Sebastian Munoz, England's Ian Poulter, American Collin Morikawa and the South Korean duo of Lee Kyoung-hoon and Im Sung-jae.
PGA Championship winner Justin Thomas was at one over, while his playoff opponent last week Will Zalatoris was a shot further back at two over.