Hunter Mahan and Russell Knox both went 6- under par on Thursday and they share the lead after one round of the Pebble Beach National Pro-Am.
Mahan played his round on the par-72 Pebble Beach Golf Links, while Knox played on the par-70 Shore Course at Monterey Peninsula Country Club.
The 156-player field rotates between those two courses and the par-72 Spyglass Hill over the first three rounds while being paired with amateur partners. Pebble Beach will host the final round.
Seung-Yul Noh had reached minus-7, but he bogeyed his final two holes for a 5- under 67. He was joined at minus-5 by Ted Potter, Jr., Matt Every, Greg Owen, Ryuji Imada and Scott Langley.
Lee Westwood, who is making his first PGA Tour start of the year, and Brandt Snedeker, who has finished second at the last two tour events, are among nine players that are two strokes off the lead at minus-4.
Defending champion Phil Mickelson carded a pair of late bogeys en route to a 1-under 69, which left him tied for 57th.
Mahan got off to a fast start with a 5-foot birdie putt at the first. He made it two in a row as his chip to the par-5 second stopped within two feet of the hole and he kicked that in.
The 30-year-old dropped his approach at the fourth to eight feet and rolled that in for his third birdie.
Mahan, who finished second at this event in 2011, again converted back-to-back birdies at six and seven. He got up and down for birdie at six, before rolling in a 14-footer birdie at seven.
He got to minus-6 with a 6-foot birdie putt at the 11th. After five pars in a row, Mahan failed to get up and down for par from a greenside bunker at the 17th.
The five-time PGA Tour winner 2-putted for birdie on the 18th to grab a piece of the lead.
"I enjoyed playing Pebble, I look forward to playing Monterey (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-5s. I hit a lot of good quality shots and hit a lot of good quality putts that didn't go in."
Knox played the back nine first on Thursday and he converted birdie chances at 11 and 12. After a bogey on No. 14, he erased that mistake with a birdie on No. 15. Knox again made it two in a row as he also birdied the 16th.
The Scotsman stumbled to another bogey at the first. Knox again atoned for that mistake quickly with a birdie on No. 2. He followed with another birdie at three.
Knox moved to minus-5 as he birdied the sixth. His final birdie came at the par-4 eighth.
NOTES: Mahan's second-place finish in 2011 was his lone top 10 in nine previous starts at this event ... Knox's 64 matched his career low on the PGA Tour, and this is the first time he has owned a piece of the lead after any round in his tour career ... Jim Herman had a hole-in-one on the par-3 12th at Spyglass ... The field for the World Golf Championship - Accenture Match Play Championship will be locked in after this week's events, including the European Tour stop in South Africa, are finished.