Los Angeles - Austin Cook, chasing a second PGA Tour title, fired an eight-under par 64 on Saturday to seize a one-stroke lead through 54 holes of the CareerBuilder Challenge in California.
Cook, who captured his first tour title in November at the RSM Classic at Sea Island, Georgia, fired seven birdies and an eagle and rolled in a tough par-saving putt at the 18th at La Quinta Country Club, one of three courses in use over the first three rounds of the tournament.
He emerged from the third round on 19-under par 197, one stroke in front of fellow americans Andrew Landry and Martin Piller, who are both seeking a first PGA Tour crown.
Overnight leader Landry had two birdies without a bogey in his two-under 70 on the Stadium Course at PGA West, where the final round will also be played on Sunday.
Piller powered up the leaderboard with a five-under 67 at La Quinta, where he teed off on 10 and after making the turn two-under picked up three straight birdies at the fifth, sixth and seventh holes.
Spain's Jon Rahm, the highest ranked player in the field at number three in the world, held a share of the lead at 19-under after birdies at the 10th and 11th on the Stadium Course.
But bogeys at 13, 15 and 17 were too much to overcome, and he signed for a two-under 70 for 199.
He was tied for fourth with Scott Piercy, who carded a six-under 66 on the Stadium Course.
Cook acknowledged that playing three courses in as many days was hard to prepare for.
"But I think I'm doing an all-right job so far," he said. "I've been able to go one shot at a time, making the birdie putts whenever they're there, giving myself a lot of opportunities."
The par putt at 18 was a "huge putt" he said.
"Put it in the fairway bunker -- we didn't think we were able to get to it but we did. Had a good up and down for par."
Despite falling back a bit, Landry was looking forward to battling for a first title on Sunday.
"I'm just going to continue doing what I've been doing," he said. "Just hitting a lot of greens and making some putts."
He planned to head out to the practice green after a tougher putting day, but put that mostly down to the differences on the putting surfaces among the courses.
"I hit a lot of really good putts today that didn't go in," he said.
The cut, made after the third round after every player had played each course, saw five-time major winner Phil Mickelson and two-time Masters champion Bubba Watson fall by the wayside. Leading third-round scores on Saturday 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)
Mickelson carded a four-over 74 to miss the cut by four strokes while Watson signed for an even-par 72 to miss it by five.
Leading third-round scores on Saturday 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)
197 - Austin Cook 63-70-64
198 - Andrew Landry 63-65-70, Martin Piller 64-67-67
199 - Scott Piercy 68-65-66, Jon Rahm 62-67-70
200 - Adam Hadwin (CAN) 66-67-67, Grayson Murray 65-68-67, Brandon Harkins 64-68-68
201 - Jason Kokrak 63-67-71, Seamus Power (IRL) 70-66-65
202 - Jhonattan Vegas (VEN) 65-69-68, Bronson Burgoon 68-66-68, John Huh 68-69-65, Kevin Kisner 67-68-67, Michael Kim 67-64-71, Kevin Chappell 71-64-67, Stewart Cink 68-69-65
203 - Charles Howell 67-70-66, Ryan Palmer 69-67-67, Brian Harman 65-68-70