Chris Kirk carded a flawless eight-under-par 63 to earn a one-stroke lead after the opening round of the OHL Classic at Mayakoba.
American Kirk birdied two of his last three holes to leapfrog Camilo Villegas atop the leaderboard in Mexico on Thursday.
A four-time PGA Tour champion, Kirk did not drop a shot as he tallied eight birdies in total at El Camaleon Golf Club.
Starting on the back nine, Kirk birdied the 13th, 14th and 15th holes and he picked up a shot at the 17th before the turn.
Kirk continued where he left off on the front nine, collecting back-to-back birdies at the second and third, and the seventh and eighth.
Villegas is tied for second alongside Gary Woodland and Ben Crane.
Colombia's Villegas had an eagle and five birdies but it was not enough to stay top heading into the second round.
Kirk is two shots clear of Webb Simpson, Aaron Wise, Scott Piercy, Kevin Streelman, Nicholas Lindheim and Abraham Ancer, who are six under through 18 holes.
A stroke further back are Luke List, Mark Wilson and Cameron Davis.
Graeme McDowell, meanwhile, made a horrendous start to his title defence.
McDowell bogeyed five holes as he posted a forgettable four-over-par 75.