The American duo of Scott Brown and Andrew Loupe are joint leaders after the opening day of the Farmers Insurance Open at Torrey Pines.
Brown recovered from two over par after six holes on the back of the South Course to finish with eight birdies in his last 11 holes, ending the day six-under-par 66.
Loupe, on the other hand, was featuring on the North Course - two shots easier than its opposing course - and also replicated Brown's round of 66, finishing with two bogies and two eagles.
Brown said he was pleased with the way he recovered towards the end of the difficult South Course.
"I hit it really good coming in," he told PGA Tour Radio. "The last 11 holes had a lot of good looks. I made a couple of lengthy putts and capitalised on the short ones. It just panned out.
"It's a hard golf course. If you're out of position, you're immediately playing for par. Fortunately I drove it good and hit a lot of good iron shots today."
Brown and Loupe have a one-stroke advantage over five players going into day two in California.
Billy Horschel, Patton Kizzire, Tom Hoge, Rob Oppenheim and Harold Varner III are all tied on five under after completing the less-challenging North Course.
Defending champion Jason Day recovered from the flu to make his tee time but failed to replicate last season's title-winning form.
The Australian went round in even par 72 despite a trio of birdies on consecutive holes on the North's back nine.
Phil Mickelson also failed to impress on his hometown course, with the three-time Major winner tied for 15th after a round of 69.
Elsewhere in the field, seven players are tied on four under, including Gary Woodland, Brendan Steele, K.J. Choi, Scott Stallings, Hideki Matsuyama, Matt Every and Chesson Hadley.