Jeff Overton has edged one shot clear of Brian Harman to lead overnight at the Frys.com Open in San Martin, California.
The 30-year-old parred the opening seven holes but a birdie at eight followed by an eagle at nine saw him reach the turn three-under-par.
Four more birdies down the back nine saw him finish six-under-par for the day, while bogeys at two and 13 saw Harman card 65 for his opening round.
There are six players tied for third on four-under-par, including regular European Tour player Brooks Koepka, while Camilo Villegas is among nine players on three-under.
Hideki Matsuyama finished the best of those who played in the Presidents Cup with a one-under round of 70. In contrast, his teammate Angel Cabrera came in four-over.