Davis Thompson tied the 18-hole scoring record at the Rocket Mortgage Classic after earning the opening-round lead.
Thompson – in his third PGA Tour tournament as a professional – carded a nine-under-par 63 to claim a two-stroke lead in Detroit, where play was suspended due to darkness on Thursday.
The 22-year-old surprisingly leads at Detroit Golf Club following a flawless first round which featured nine birdies to match the 18-hole scoring record at the event, joining Nate Lashley and J.T. Poston (both in 2019).
"Sounds good on Sunday," Thompson said afterwards, having been a collective six-over par in his six previous starts on tour (four as an amateur). "It's only Thursday. I know I've got a long way to go."
"I’ve played in a few pro events now, so you've just got to keep your emotions in check," Thompson said. "Anything can happen. I know I'm playing well, so I'm just going to have some confidence going into [Friday] and hopefully I can play another good round."
Brandon Hagy, Tom Lewis and Joaquin Niemann are two shots off the pace heading into Friday's second round, while Seamus Power and J.J. Spain are a stroke further back.
Former world number one Jason Day ended the opening day five under following his 67 as six-time major champion and US PGA Championship winner Phil Mickelson posted a 69 to be level with the likes of Patrick Reed.
Masters champion Hideki Matsuyama opened his tournament with a two-under-par 70.
As for defending champion Bryson DeChambeau, the big-hitting American shot an even-par 72.
Trying to successfully defend a PGA Tour title for the first time, world number six DeChambeau mixed three birdies with three bogeys.
It comes as DeChambeau and caddie Tim Tucker take some time apart.
"They have gone their separate ways for now," DeChambeau's agent Brett Falkoff told ESPN. "That doesn't mean forever, but it means they are not working together now. They met last night and decided to move on.
"It's just an accumulation of things, and it's never easy when a player and caddie split up. They just decided the best situation for now was essentially to not be together anymore."