A birdie-blitz from Cameron Percy has the Australian just one off the lead after the first round of the PGA's Safeway Open.

Percy is in a three-way tie for second with Sam Burns and Bo Hoag, one behind Russell Knox who shot a nine-under 63 on Thursday in the first event of the new PGA Tour season.

The Victorian made three consecutive birdies to get into contention at the turn, then birdied both of the par fives on his back nine to keep the heat on Knox.

After missing the FedExCup playoffs by two spots to close last season, Knox had seven birdies and eagled the 550-yard, par-five fifth hole.

Two-time Safeway Open champ Brendan Steele and Pat Perez posted 65s to be joint fifth.

Knox is seeking his first victory since 2016 when he captured both the World Golf Championships-HSBC Champions and Travellers Championship for his only PGA Tour wins.

Historically a slow starter, the 35-year-old Scot had the first-round lead at Silverado Resort despite more early struggles.

He hit his first tee shot of the day into the rough and had to scramble for par. After two-putting on the par-three second hole, Knox left his approach on No.3 41 feet short of the pin, forcing another two-putt.

A birdie on No. 4 got Knox back on track and the eagle on No.5 jump-started his rise up the leaderboard.

"I knew this week that par-five scoring would be big to your ultimate performance," Knox said.

Knox was admittedly disappointed by missing out on the FedExCup playoffs - he had qualified the previous six years - but used the time off to prepare for the Safeway Open while adjusting to new coach Mark McCann.

"I've worked as hard as I ever have the last two weeks before this event, so it's really nice to see something good happen immediately," Knox said.

Phil Mickelson, playing a warm-up before next week's US Open at Winged Foot, shot 71.

"The best way to get ready for Winged Foot is to play well here," Mickelson said. "These fairways are tighter and more difficult to hit than what we'll have next week.

"But the rough is going to be a lot more penalising next week so it's a great way to work on driving, work on your golf swing."

Australian Cameron Davis is tied 81st after shooting one-under while Rhein Gibson was one over for the round.