Russell Knox matched his career low on the PGA Tour by firing a six-under par 64 to seize a share of the first-round lead at the Pebble Beach National Pro-Am.
Knox, who birdied four of his final eight holes on the Shore Course on Thursday, shares the lead at six-under with American Hunter Mahan, who played the Pebble Beach Golf Links course.
The 156-player field rotates between three courses in the first three rounds, comprising Spyglass Hill, Shore and Pebble Beach, while playing with amateurs. Pebble Beach will host the final round.
The 27-year-old Scotsman Knox played the back nine first on Thursday, making birdie at 11 and 12.
After a bogey on No. 14, he rolled in another birdie on No. 15 and then made it two in a row as he also birdied the par-four No. 16.
Knox moved to five under by making birdie at the sixth, and his final birdie of the day came at the par-four eighth.
Five-time PGA Tour winner Mahan needed a two-put for birdie on the 18th to grab a share of the lead.
"I enjoyed playing Pebble. I look forward to playing Monterey (Shore course on Friday)," Mahan said.
"Pebble isn't long, so you can attack some holes out here, and I was able to do that and I was able to get some short clubs and able to take advantage of the par-fives.
"I hit a lot of good quality shots and hit a lot of good quality putts that didn't go in."
South Korea's Noh Seung-Yul bogeyed his final two holes for a five-under 67. He was joined at minus-five by England's Greg Owen, Japan's Ryuji Imada and three others.
Lee Westwood and Brandt Snedeker, who has finished runner-up at the last two tour events, are among nine players that are two strokes off the lead at minus-six. Westwood is making his first PGA Tour start of the year.
Defending champ Phil Mickelson is tied for 57th after shooting a pair of late bogeys en route to a one-under 69.
Mickelson is coming off a victory last week in Phoenix.