Jerry Kelly and Steve Stricker shot a brilliant 56 in the first round of the Franklin Templeton shootout at the Tiburon Golf Club in Naples, but they only lead by one stroke.
Kelly and Stricker posted gains on all but three of the 18 holes in the scramble format in Naples, adding an eagle on the eighth to their 14 birdies, eight of which came on the back nine, to finish the day on 16 under.
Hot on their heels are Harris English and Matt Kuchar, the pair making a late charge to pull two shots clear of third-placed duo Charles Howell III and Rory Sabbatini after being 13 under through 16 holes.
There was nothing to separate the pairs of Kevin Chappell and Kevin Kisner, Luke Donald and Russell Knox and Jason Dufner and Brandt Snedeker, all of whom finished the first round on 12 under for a share of fourth.
Bryson DeChambeau, who was using a new side-saddle putting grip, and Lexi Thompson sit one shot behind Charley Hoffman and Billy Horschel in eighth after carding a 10-under 62, and the leaderboard is propped up by four pairs on nine under.