Los Angeles - Andrew Landry fired seven birdies in a seven-under par 65 on Friday to seize a one-stroke lead over world number three Jon Rahm in the PGA CareerBuilder Challenge in California.
Landry nabbed five of his seven birdies on the back nine at the Nicklaus Tournament Course at PGA West - one of three in use over the first three days of the event in La Quinta in the desert east of Los Angeles.
Landry, ranked 184th in the world and in search of his first US PGA Tour title, missed just three greens in regulation and has yet to make a bogey this week.
His 16-under total of 128 put him one ahead of Spain's Rahm, the overnight leader after a sizzling first-round 62 who carded a 67.
Rahm teed off on the 10th on the Nicklaus Tournament Course. He opened with back-to-back birdies before a bogey at the 12th, He sandwiched two more birdies at 13 and 15 around a bogey at 14 before notching three more birdies coming in.
"I wasn't as pure as yesterday," Rahm said. "Everything was just a little bit off."
It was a further stroke back to American Jason Kokrak, who had six birdies in a five-under 67 on the Nicklaus Tournament Course.
Two-time major winner Zach Johnson led a group sharing fourth on 131 alongside Michael Kim and Martin Piller. Johnson and Kim both carded 64s on the Nicklaus Tournament Course, where Kim notched an eagle and six birdies without a bogey, Piller posted a 67 on the Stadium Course.
"Doing a lot of good things," Johnson said. "If we're going to pick apart a weakness it's probably I haven't been putting great ... but ball strike's good. I'm hitting my driver in the fairway, I'm getting more loft into these greens the last two weeks than I've ever been accustomed to."
Five-time major-winner Phil Mickelson, making his 2018 debut, carded a 68 on the Nicklaus course to find himself 10 off the pace.
"I've been pretty pleased, overall, with the way I've been driving the ball, and very displeased with the way my iron game has been," Mickelson said.
"Usually my iron play is a lot better than what it's been," added Mickelson, who has hit just 21 of 36 greens in regulation over the first two rounds.
"So I'll go work on it and hopefully improve each round ... I feel like if I continue to drive the ball the way I am, and if I got my iron play back to my normal standard, I should have the results that I've been expecting."
Leading second-round scores on Friday in the US PGA Tour CareerBuilder Challenge, played on the La Quinta Country Club, Nicklaus Tournament Course and Stadium Course at La Quinta, California (USA unless noted, par-72)
128 - Andrew Landry 63-65
129 - Jon Rahm (ESP) 62-67
130 - Jason Kokrak 63-67
131 - Zach Johnson 67-64, Michael Kim 67-64, Martin Piller 64-67
132 - Nick Watney 65-67, Brandon Harkins 64-68, Brian Gay 68-64
133 - Austin Cook 63-70, Kevin Na 66-67, Adam Hadwin (CAN) 66-67, Scott Piercy 68-65, Brian Harman 65-68, Russell Knox (SCO) 69-64, Grayson Murray 65-68, Aaron Wise 64-69, Beau Hossler 64-69
134 - Richy Werenski 67-67, Lucas Glover 66-68, James Hahn 68-66, Peter Uihlein 70-64, Jhonattan Vegas (VEN) 65-69, Bronson Burgoon 68-66, Hudson Swafford 66-68, Maverick McNealy 66-68, Trey Mullinax 70-64