RIO GRANDE, 5 Mar 2015 (AFP) - Hubbard, who teed off on the 10th hole at Trump International Golf Club, had two birdies and a bogey in his first nine holes, and defied the windy weather as he got hot coming in.
He birdied three in a row from the fourth, and after a bogey at eight seized a one-shot lead with a birdie at the par-four ninth.
"It played tough out there with the wind," Hubbard said. "I actually probably played the into the wind holes better than the downwind holes where I had to just hit normal shots."
Hubbard, making his 11th start of the season and the 13th of his career, is trying to improve on his best previous US PGA Tour finish, a tie for 20th at the Humana Challenge.
He had a one-stroke edge over Americans Chris Smith and Billy Mayfair and Argentina's Emiliano Grillo.
Former world number one David Duval headlined a group of 11 players on two-under 70, which also included Australian Rod Pampling, Spain's Rafael Cabrera and Germany's Alex Cejka.
Zimbabwe's Brendon De Jonge, the top-ranked player in the field at 87th in the world, headed a group of 10 players on 71, a bunch that also included defending champion Chesson Hadley.
The tournament featuring the tour's lesser lights is opposite the World Golf Championships Cadillac Championship at Doral in Florida, where most of the top players in the world are teeing it up this week.
Leading first-round scores on Thursday in the $3 million US PGA Tour Puerto Rico Open (USA unless noted, par-72)
68 - Mark Hubbard
69 - Chris Smith, Billy Mayfair, Emiliano Grillo (ARG)
70 - Dicky Pride, J.J. Henry, David Duval, Chad Collins, Scott Pinckney, Jon Curran, James Driscoll, Jonathan Byrd, Alex Cejka (GER), Rod Pampling (AUS), Rafael Cabrera (ESP)
71 - Jason Gore, Jerry Kelly, Eric Axley, Michael Bradley, Brandon Hagy, Andrew Svoboda, Chesson Hadley, Josh Teater, Shaun Micheel, Brendon De Jonge (ZIM)