American Chez Reavie is a stroke clear after the first round of the AT&T Pebble Beach Pro-Am.
Reavie carded an eight-under-par 63 to earn an early lead at the PGA Tour tournament on Thursday.
A Tour winner back in 2008, Reavie nailed the back nine with five birdies and an eagle, after completing the front nine at one under, to cap a successful opening round.
Reavie's round was the standout on a day of some high-quality golf with Swede Freddie Jacobson, Australian Cameron Smith and compatriot Bronson Burgoon a shot adrift.
Burgoon was in the lead after playing the back nine first and matching Reavie's five birdies and an eagle, but could only manage par following the turn to finish the day tied for second.
Justin Rose, Dawie van der Walt, Robbie Castro, Rickie Barnes, Shane Bersch, J.B. Holmes and Spencer Levin are all tied for fifth at six under.
Four-time champion Phil Mickelson carded a first-round 68, while defending champion and two-time winner Brandt Snedeker finished even par.
Mickelson holed three birdies on the front nine, before a bogey on the eighth brought him back to two under, but he recovered well to card another two birdies on the back nine.
Snedeker shot bogeys at holes six and eight on his front nine, which were cancelled out by birdies at the fifth and seventh and it was a similar story on the back nine where a birdie at the 18th saw the American drop to par.
World number one Jordan Spieth, meanwhile, finished the day at one under.
Spieth had a mixed bag with four birdies and three bogeys to be seven shots off the lead.