Not because he's the World No.411, but because he's hardly touched the clubs in two months during a nightmare winter in his adopted home of Raleigh, North Carolina.

The 43-year-old fired a five-under-par 66 at Monterey Peninsula Country Club to sit two shots back of leaders Kevin Streelman (65, Spyglass) and Beau Hossler (65, Pebble Beach) at seven under.

Sharing sixth alongside World No.1 Dustin Johnson, who shot a 67 at Spyglass Hill, Percy admits he was rusty.

"I have only played golf three times in eight weeks," Percy said.

"I've been at home in Raleigh and we've had one of our worst winter snowstorms in history, so I've had no practice and I'm trying to catch up.

"Maybe my expectations weren't very high and I played well because of that."

Jason Day is next best of the Australians courtesy of a 69 at Spyglass leaving him at three under, sharing 32nd with a logjam of players including five-time major winner Phil Mickelson.

Coming off a win in his last PGA Tour start at Torrey Pines, World No.10 Day says he needs to contain his enthusiasm if he is to go low on the easier Monterey course in Friday's second round.

"I was anxious, man. Probably almost too excited; I wanted the tournament to start on Tuesday," said Day, who squandered a solid chance to win at Pebble Beach last year.

“Monterey is one of those courses where you can get after it, so I'm excited but I've got to take my time and ease myself into it."

Four-time major winner Rory McIlroy opened his US season with a 68 at Spyglass to share 16th at four under with a host of players including World No.2 Jon Rahm.

Rod Pampling (69) is two under, while fellow Australians Greg Chalmers and Aaron Baddeley are one-under the card after each shot a 70.

Recent Australian winner Cameron Davis (73, Pebble Beach) and Stuart Appleby (73, Spyglass) are one over, while Sydney native Matt Jones (74, Pebble Beach) is two over.

Defending champion Jordan a Spieth shot an even-par 72.