Davis Thompson, in his third PGA Tour event as a professional, tied a Detroit Golf Club record with a 9-under 63 to take the early first-round lead in the Rocket Mortgage Classic.
Brandon Hagy and Tom Lewis were two shots back. Seamus Power and J.J. Spaun shot 66, putting them another stroke behind the surprising leader.
Thompson is in the field as a sponsor exemption. The 22-year-old former University of Georgia star missed the cut last week at the Travelers Championship after tying for 35th in his pro debut at the Palmetto Championship earlier in June.
It is unlikely anyone saw his breakthrough round coming after he was a combined 6-over par in six previous starts — four as an amateur — on the PGA Tour. Thompson did show a flash of promise when he competed in the 2020 U.S. Open as an amateur, opening with a 69 before missing the cut at 7-over 147.
Thompson took advantage of favorable conditions with rain-softened greens and light wind Thursday morning at Detroit Golf Club, missing only one green and needing just 26 putts in his bogey-free round with nine birdies. He resumed his round after play was suspended due to inclement weather for three-plus hours.
Thompson matched the course record shared by Nate Lashley, who won the inaugural event in 2019, and J.T. Poston.
Players with afternoon tee times had to endure a long wait to begin playing and wind that was 5 to 10 mph stronger than it was in the morning.
Defending champion Bryson DeChambeau got off to a shaky start, a day after parting ways with caddie Tim Tucker. He replaced him for this week with Cobra-Puma Golf tour operations manager Ben Schomin, who said he was a caddie in competition for the first time.
DeChambeau, No. 6 in the world ranking, is trying to win a PGA Tour event in consecutive years for the first time. He had a chance two weeks ago to repeat at the U.S. Open, but went from leading the major with nine holes left to faltering and finishing in a tie for 26th.
And now, the big hitter might not make the cut and that would be a blow for him and the Detroit-based company that pays him as part of an endorsement deal.
DeChambeau missed the fairway to the right at Nos. 2 and 3, leading to bogeys. At the par-3, 184-yard ninth hole, he was short off the tee, on his chip and 10-foot putt to put another bogey on his card that dropped him to even-par 36 at the turn.
Phil Mickelson entered the Rocket Mortgage Classic for the first time in the event's three-year history and said it will be his last appearance.
Mickelson said he will not come back due to what he called an "unnecessary attack," in a report by The Detroit News that was published earlier in the week. The newspaper obtained federal court records from 2007, detailing how a Michigan-based bookie was accused of cheating Mickelson out of $500,000.
The 51-year-old Mickelson shot a 69, marking the sixth time he has been under par out of 11 rounds since he became the oldest major winner at the PGA Championship in May.