Los Angeles - Scott Brown and Andrew Loupe shared the first-round lead at Torrey Pines on Thursday on six-under par 66 as defending champion Jason Day struggled in the $6.5 million US PGA Tour Farmers Insurance Open.
Australia's Day, ranked second in the world, had skipped Wednesday's pro-am at the venue north of San Diego with flu-like symptoms.
He got off to a good start on the Torrey Pines North Course, teeing off on 10 and nabbing birdies at 13, 14 and 15. He bounced back after bogeys at 17 and the first with a birdie sat the second, but back-to-back bogeys at seven and eight saw him finish the day tied for 76th.
Rickie Fowler, who has ascended to number four in the world on the strength of an impressive victory in the Abu Dhabi HSBC Golf Championship on Sunday, fired an opening 73 that included a double-bogey and three bogeys on the North Course, the easier of two layouts in use over the first two rounds of the tournament.
Brown's round was all the more impressive coming on the South Course.
Brown, whose only prior PGA Tour win came at the 2013 Puerto Rico Open, surged up the leaderboard with eight birdies in his last 11 holes, including four in his last five.
"I hit it really good coming in," Brown said. "Had a lot of good looks, made a couple of lengthy putts and capitalized on the short ones.
"It's a hard golf course," Brown added. "If you're out of position you're immediately playing for par."
Loupe notched his 66 on the North Course, which played more than two strokes easier than the South.
Loupe seized his share of the lead with an eagle at the par-five 18th. It was a perfect bookend to a round he opened with an eagle at the par-five first, and in between he had four birdies and two bogeys.
The leading duo were one stroke in front of a group of five players. Billy Horschel, Patton Kizzire, Tom Hoge, Rob Oppenheim and Harold Varner all carded their 67s on the North Course.
South Korean veteran K.J. Choi and Japan's Hideki Matsuyama were among a group sharing eighth on 68 that also included Americans Gary Woodland, Brendan Steele, Scott Stallings, Matt Every and Chesson Hadley.
Five-time major winner Phil Mickelson shook off a double-bogey at the second hole of the South Course and capped his round with a birdie at 18 to join a big group on 69.
Mickelson's six birdies on the day included three in a row from the 13th, and after a bogey at 17 he responded by rolling in a 27-foot birdie putt at the last.
Although he was headed to the easier of the two courses on Friday, Brown said he wasn't expecting the North to be a pushover.
"The rough is still thick over there," he said. "You've still got to drive it good to score over there.
"I'll just try to continue to drive it good and hopefully make some more birdies over there."
Leading first-round scores on Thursday in the $6.5 million US PGA Tour Farmers Insurance Open at Torrey Pines in San Diego, California (USA unless noted, par-72):
66 - Scott Brown, Andrew Loupe
67 - Billy Horschel, Patton Kizzire, Tom Hoge, Rob Oppenheim, Harold Varner
68 - Gary Woodland, Brendan Steele, K.J. Choi (KOR), Scott Stallings, Hideki Matsuyama (JPN), Matt Every, Chesson Hadley
69 - Martin Laird (SCO), Carlos Ortiz (MEX), Brian Harman, Patrick Reed, Kyle Stanley, John Huh, Kyle Reifers, Paul Dunne (IRL), Ollie Schniederjans, Freddie Jacobson (SWE), Cameron Tringale, Jim Herman, Kevin Streelman, Jimmy Walker, Phil Mickelson, Smylie Kaufman, Steve Marino, Hiroshi Iwata (JPN), Tyrone Van Aswegen (RSA)