Tommy Gainey edged into a one-stroke lead with a strong finish to the first round of the Puerto Rico Open in Rio Grande.
The 45-year-old American shot a seven-under 65, sinking five birdies on his last seven holes to make a late surge to the top of the leaderboard.
Gainey got off to a dream start with three birdies on his first four holes before being slowed by a pair of bogeys, but the world number 458 rallied to close out in style.
Robert Garrigus had set the early pace at the Grand Reserve Country Club, climbing to seven under, but a bogey on the ninth – his final hole – spoiled a clean round as he slipped to equal second place.
Garrigus was one of seven players left holding a share of second at the close of play, with Canada's Taylor Pendrith and American Lee Hodges also carding six-under 66s.
They were joined by home favourite Rafael Campos, Argentina's Fabian Gomez, Brandon Wu of the United States and Greg Chalmers of Australia, who hit a hole in one at the eighth.
Belgium's Thomas Pieters is joint 25th, carding a three-under 69, while another European Tour star in search of a first PGA Tour win, Matt Wallace, slumped to a four-over 76 after a double bogey at the 15th.
His fellow Englishman and three-time PGA Tour winner Ian Poulter fared better, going around for a one-under 71, one stroke behind Europe's Ryder Cup captain Padraig Harrington, with the Irishman carding 70.