American Brian Stuard carded a six-under 66 to take the early lead at the Puerto Rico Open on Thursday.
Stuard was seven under through 12 holes at a windy Trump International Golf Club in Rio Grande, but had to settle for a one-shot lead after bogeying the par-four seventh.
Jason Gore, also of the USA, and New Zealand's Danny Lee carded five-under 67s to be closest to Stuard.
Gore went bogey free and shot five birdies, while Lee responded to a bogey on the par-three sixth to shoot four birdies thereafter.
A group of seven players are tied for fourth spot on four under, with YE Yang of South Korea joining American contingent Tim Petrovic, Ricky Barnes, Chesson Hadley, William McGirt, Eric Axley and Ben Martin with opening rounds of 68.
Yang birdied two of his last four holes to sit in the top 10, as he chases his first trophy on the tour since winning the PGA Championship in 2009.
But that is nothing compared to the backlog on three under, with 21 players all signing off on rounds of 69.
Among those are Spaniards Rafael Cabrera Bello and Alvaro Quiros, Australia's Steven Bowditch and South Africa's Tyrone Van Aswegen.
Defending champion Scott Brown is tied for 32nd on two under, four shots off the pace.