Kevin Na fired an eight-under 62 to grab the first-round lead at the Fort Worth Invitational as Jordan Spieth made a solid start.
Na, who finished tied for sixth at the AT&T Byron Nelson, managed a bogey-free round including an eagle and six birdies Thursday.
The American is a shot clear of Charley Hoffman (63) at Colonial Country Club in Fort Worth, Texas.
Spieth, playing in his home state for the second straight week, opened with a one-under 69.
The three-time major champion has top-two finishes – including a win in 2016 – in his past three starts at Colonial.
But Spieth, who is winless this year, was unable to get going in the first round, mixing three birdies with two bogeys.
Emiliano Grillo, Jhonattan Vegas, Andrew Putnam and Beau Hossler had more success, shooting six-under 64s.
Justin Rose produced a strong finish to his round with four birdies in five holes on the back nine to sit at four under.
Rickie Fowler is a shot further back and ahead of Jon Rahm, who was runner-up last year and opened with a 68.
Defending champion Kevin Kisner struggled in the first round, shooting a two-over 72.
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