Tommy Gainey birdied five of his final seven holes in the opening round of the Puerto Rico Open for a 65 and a one shot lead over seven others, including local favourite Rafael Campos.
The 45-year-old American also had four birdies on the front nine to go with two bogeys to reach seven under in windy conditions at the Grand Reserve Country Club.
Campos is tied with Robert Garrigus, Taylor Pendrith, Lee Hodges, Greg Chalmers, Fabian Gomez and Brandon Wu, who all shot 66.
South Africa's Branden Grace is among seven players who shot 67 to sit two shots off the pace.
Gainey got off to a fast start Thursday, birdieing the opening two holes and three of the first four.
"It's windy. It's Puerto Rico," Gainey said. "I'm just glad that it's 80 degrees outside, because back in South Carolina, all it is, is 40 degrees and raining. So I'm just glad to be in some hot weather. Wind, I can deal with. But I just hit it really good today."
Campos is seeking his third top-10 finish in 12 starts in the event.
There are no players ranked in the top 50 in the world in the field because it is being held the same week as the World Golf Championships at The Concession Gold Club in Bradenton, Florida.
But the stakes are high for the winner, who receives 300 FedEx Cup points, a two-year PGA Tour exemption and an invitation to the PGA Championship in May.
Last year's winner, Viktor Hovland, isn't taking part because he is competing in the WGC tournament.
The event is being played without spectators because of the coronavirus pandemic.
Gainey cooled off after his hot start. He made bogey on No. 11 and then got hot again, rolling in birdies on the par-four 12, par-four 13th, par-five 15th, par-four 17th and par-five 18th.
"Really happy at bouncing back with a birdie on 12," he said. "Just showing a little resilience and confidence to come back from a bogey, because when you three-putt from 12 feet, come on, let's be honest, that's bad."
European Ryder Cup captain Padraig Harrington shot 70. Ian Poulter, the top-ranked player in the field at 59th, opened with a 71.
The next stop on the US Tour is the Arnold Palmer Invitational at the Bay Hill Club in Orlando.
Leading first-round scores on Thursday in the US PGA Tour Puerto Rico Open in Rio Grande (USA unless noted, par-72):
65 - Tommy Gainey
66 - Robert Garrigus, Rafael Campos (PUR), Taylor Pendrith (CAN), Lee Hodges, Greg Chalmers (AUS), Fabian Gmez (ARG), Brandon Wu
67 - Brice Garnett, Josh Teater, Branden Grace (RSA), Cameron Percy (AUS), Andrew Putnam, Mark Anderson, Dalton Ward