Former Open champion Francesco Molinari is one shot off the pace after the first round of his Safeway Open debut, with Adam Scott and Andrew Landry leading the pack on seven under par.
Scott, starting on the back nine, had a steady first nine holes with a bogey on the par four-13th the only blot on his copy book at the turn. Two birdies and an eagle on the front nine secured the Australian a round of 65.
Landry, meanwhile, put together five birdies in his first nine holes and two more in the second half of his round to share top spot in Napa, California.
Molinari, who finished 14th in the defence of his BMW PGA Championship title at Wentworth last week, shot 66 including a sublime tee shot on the 15th which landed 10 feet from the pin.
Defending champion Kevin Tway had a steady start with a round of 71 only good enough for a share of 51st place, while two-time champion Brendan Steele's 74 left him tied for 116th.