Northern Ireland's Graeme McDowell and his partner Emiliano Grillo hold a three-way share of the lead following the opening round of the QBE Shootout in Florida.
McDowell and Argentinian Grillo carded 12 birdies and an eagle at Tiburon Golf Club in Naples to leave themselves 13 under par on 59.
American duo Patton Kizzire and Brian Harman join them at the top of the leaderboard going into the final two days, alongside compatriot Bryson DeChambeau and his South Korean partner Kevin Na.
Tony Finau and Lexi Thompson sit two strokes off the pace on 11 under. Luke List and Charles Howell III are also on 61 strokes, with Gary Woodland and Charley Hoffman joining the three-way tie for fourth place.
Reigning champions Sean O'Hair and Steve Stricker began their title defence with a first-round score of 62 which leaves them three strokes off the lead and tied for seventh place with Bubba Watson and Harold Varner III.
Play for the 12-team field continues with an alternate shot format on Saturday, before a four-ball format concludes the event on Sunday.