Snedeker and Choi lead the way
Defending champion Brandt Snedeker shared the lead with KJ Choi after the first round of the Farmers Insurance Open.
Both players carded 65 at Torrey Pines to lead the rest of the field by one stroke.
England's Ross Fisher was in a large group at six under along with Charles Howell III and Canadian veteran Mike Weir in La Jolla, California.
Ryder Cup player Snedeker sank seven birdies in a flawless round of 65 on the north course to set a pace which was eventually matched by Choi after a blistering finish.
Playing the south course and starting from the 10th hole, the Korean birdied three of his last four holes - having earlier finished the back nine with five birdies and a bogey up to the turn.
Fisher, playing two groups behind Snedeker, bogeyed his second hole of the day but surged back with seven birdies to put himself among eight players a shot off the lead.
Howell's fellow Americans Josh Teater, Luke List, Billy Horschel and Scott Stallings and Weir's compatriot Adam Hadwin complete the group.
England's David Lynn shot a five-under-par 67 on the north course to nestle among a 10-strong group at five under which also included Tag Ridings, who provided the day's highlight with a hole in one on the par-three third.
Tiger Woods was a further shot back after two bogeys in the last four holes, having earlier produced an excellent eagle at the sixth hole as he looked to improve on last week's showing at the Abu Dhabi Championship, where he missed the cut.
Ryo Ishikawa and Vijay Singh were further big names at four under while the huge group at three under contained a host of recognisable figures.
Europeans Nicolas Colsaerts and Robert Karlsson both shot 69 as did a strong American contingent including Lucas Glover, Bill Haas, Hunter Mahan, Dustin Johnson and Nick Watney.
But Phil Mickelson was back at level par alongside Scotland's Martin Laird.