LA JOLLA -- Americans Scott Brown and Andrew Loupe share a one-shot lead over five golfers, including three PGA Tour rookies, entering Friday's second round of the $6.5 million Farmers Insurance Open at Torrey Pines Golf Course in La Jolla.
Brown and Loupe on Thursday both shot six-under-par 66s, Brown on the harder South Course, Loupe on the North Course. Among the first-round's seven lowest scores, only Brown's came on the South Course.
The scoring average on the South Course was 73.359 strokes. The scoring average on the North Course was 70.897.
Billy Horschel, Tom Hoge and PGA Tour rookies Patton Kizzire, Rob Oppenheim and Harold Varner III are tied for second at five-under-par 67.
A rookie has never won the Farmers Insurance Open. Gene Littler won the event as an amateur in 1954.
Defending champion Jason Day of Australia, second on the Official World Golf Ranking, shot an even-par 72 on the North Course and is tied for 76th. He missed Wednesday's pro-am because of a bout with the flu.
San Diego native Phil Mickelson shot a three-under-par 69 on the South Course, putting him in a 19-way tie for 15th, three shots off the lead.
The group at three-under-par also includes Ireland's Paul Dunne, who was making his PGA Tour debut as a professional. As an amateur, Dunne shared the lead after third round of last year's British Open, then shot a final-round six-over-par 78 at St. Andrews to finish in a tie for 30th.
Xander Schauffele, a San Diego State and Scripps Ranch High School alumnus who is playing in the tournament for the first time, shot a three-over- par 75 on the South Course.
Since 2000, no first-round leader or co-leader has gone on to win the Farmers Insurance Open.
Brown began his round on the back nine, shooting an even-par 36, with what he called "a couple stupid bogeys" on the par-5 13th hole, where he hit a ball in the hazard, and the par-4 15th.
Brown birdied the par-4 17th and par-5 18th and shot a six-under-par 30 on the front nine with six birdies.
"The last 11 holes I had a lot of good looks and made a couple of lengthy putts and capitalized on the short ones," the 32-year-old Brown said after leading or sharing the lead in a PGA Tour event for the first time in his 112 starts. "Started off hitting it good, just couldn't get anything in."
Brown missed the cut in last week's CareerBuilder Challenge and in each of his three previous appearances in the Farmers Insurance Open. He has one PGA Tour victory, the 2013 Puerto Rico Open.
Loupe began his round with an eagle on the North Course's par-5 first hole and ended it with an eagle on the par-5 18th.
"Quite the day," the 27-year-old Loupe said. "That doesn't happen very often. Fortunately, I was just able to hit the fairway on both those par- 5s and it was shorter over there on the North Course so I had irons in my hand and I was able to hit a couple good ones in there."
In between his eagles, Loupe had four birdies and bogeys on the par-4 second and par-4 13th in what he called a "really solid" round.
"I hit my irons pretty well for the most part," said Loupe, who tied for third in the CareerBuilder Challenge, the best finish in his 44 PGA Tour starts.
"When you drive it well on the North Course, you can flip some of those par-4s around and have some wedges in and I think that's what I was able to do."
The 156-player field is split between the South and North courses over the first two rounds. Players who played the South Course on Thursday will play the North Course today, while players who played the North Course on Thursday will play the South Course today.
The field will be reduced to the low 70 plus ties following the conclusion of today's play. The final two rounds will be played exclusively on the South Course. The winner will receive $1.17 million.