JT Poston carded a brilliant 62 as he took the lead at the John Deere Classic on Thursday.
Poston, 29, produced seven birdies as well as an eagle on the fifth hole in a bogey-free opening round.
It was a continuation of his recent fine form that saw him tie for second place at Traveller's Championship in Connecticut last week.
It also saw him become the first player on record (since 1983) to open consecutive PGA Tour events with a 62 or better.
"I looked at [caddie Aaron] Flener like, 'Did that really happen?'" Poston said. "I mean, it's kind of one of those - I think it was the first green that I missed, and to hole it out and make birdie is just kind of - you're not really thinking you're going to make it, but when you do, you just realize it could be one of those days."
Michael Gligic from Canada finished in second at 64 in the final group of the day off the first tee - followed by Vaughn Taylor and Christopher Gotterup at 65.
"I never really got into trouble," Gligic said. "Hit a lot of fairways. Hit I think maybe 17 or 16 greens and just never really got into too much trouble.
"Yeah, just giving myself a lot looks. Some of them fell, and hopefully we can do that tomorrow."
Meanwhile, Ricky Barnes, Denny McCarthy, Chris Naegel and Dylan Frittelli shot 66.
Gligic opened this year's event with a bogey-free 7-under 64, good for his career-low in his 70th Tour start. The Canadian had missed the cut in his first start at the John Deere Classic in 2021.
Poston won the 2019 Wyndham Championship for his lone PGA Tour title.
United States' Ryder Cup captain Zach Johnson and the 2012 winner, opened with a 69 in his 20th consecutive start in the event.