Former champion Jordan Spieth was three shots back as Camilo Villegas led the field on day one of the Valero Texas Open.
Starting on the back nine, Columbia's Villegas came home in style by making four straight birdies from his 11th to 14th holes before nailing another on his last to finish with an eight-under 64.
"You know what, some days the hole is a little bit big and that was the case today," Villegas said.
"I played really good, but I also got a couple nice breaks, made a couple good par saves and overall it was very solid.
"Obviously you don't shoot eight under not playing good. No, I'm excited. I like this place. But it's only Thursday, so we've just got to keep patient, keep doing what we're doing and have fun out there."
The round represented a departure in form for Villegas, who has made just one cut in the past seven events he has entered. He did, however, finish tied for eighth in the Honda Classic two weeks ago in Florida.
Two strokes behind were Sung Kang and American Cameron Tringale, whose compatriot Spieth led the morning finishers despite ending with a bogey three for a five-under 67.
European Ryder Cup captain Padraig Harrington is in a share of 13th place after shooting a round of 70, Northern Ireland’s Graeme McDowell carded a 74.