La Quinta - Rookie James Hahn and Roberto Castro maintained their lead by shooting five-under 67s in the second round of the PGA Tour's $5.6m Humana Challenge on Friday.
Hahn and Castro are both chasing a first PGA Tour victory and are at 14-under par.
"Same situation as yesterday, my playing partner was making a bunch of birdies too and we both kind of got going and had the mojo going the right way, so it was a good day," Castro said.
"I played well all day. Some nice up-and-downs on the par-fives for birdies, a couple slipped away there at the end.
"Yesterday I made a 50-footer on the last on a good putt. Today I felt like I hit a good putt and three-putted. So that stuff is going to even out over 72 holes."
Hahn had an eagle and a nice birdie stretch in the second half of his round.
"I started off slow," Hahn said. "But I hit some good shots and had a stretch of a birdie, eagle, birdie, and that was pretty much my round."
Just one stroke back were Darron Stiles, Scott Stallings and Richard H. Lee who each shot 65 and moved into a tie for third place.
Jason Kokrak had shared the first-round lead with Castro and Hahn. Kokrak shot 69 on Friday and dropped into a tie for sixth place at 12-under with eight others.
Joining Kokrak were rookies Lee Williams and David Lingmerth, Zach Johnson, Kevin Stadler, Charles Howell, Charley Hoffman and Australia's Aaron Baddeley and Greg Chalmers.
The best rounds among that group came from Lingmerth (64) Williams (65) and Howell (65), all on the Nicklaus Course.
Phil Mickelson, who has been battling a virus, rebounded on the second day for a 67, following up a first-round 72.
Mickelson rolled in seven birdies and had a pair of bogeys on Friday.
"The last two holes was the first time that I actually hit solid shots and my rhythm felt good and I made good swings," said Mickelson, who is making his season debut.
"I've been quick from the top, my rhythm has been off, and I've hit a bunch of squirrely shots.
"I made a lot of rusty mistakes, like that three-putt there, but it feels a lot better, the last couple holes feel a lot better, I'm looking forward to tomorrow's round."
Last week's winner Russell Henley remained in contention at 11-under. Henley had four birdies and an eagle in the second round.
The cut will come on Saturday, after everyone has played each of the three par-72 courses in use over the first three rounds.
Leading second-round scores on Friday in the $5.6m US PGA Tour Humana Challenge on the Palmer Course, Nicklaus Course and La Quinta Country Club course (USA unless noted, all courses par-72):
130 - Roberto Castro 63-67, James Hahn 63-67
131 - Darron Stiles 66-65, Scott Stallings 66-65, Richard H. Lee 66-65
132 - Lee Williams 67-65, Jason Kokrak 63-69, Zach Johnson 66-66, David Lingmerth (SWE) 68-64, Kevin Stadler 66-66, Charles Howell 67-65, Charley Hoffman 65-67, Greg Chalmers (AUS) 64-68, Aaron Baddeley (AUS) 64-68
133 - Daniel Summerhays 65-68, Stewart Cink 66-67, Ricky Barnes 65-68, Robert Garrigus 66-67, Russell Henley 64-69, Brian Gay 67-66, Bud Cauley 70-63