William McGirt is the surprise leader after the third round of the Northern Trust Open at Riviera in California.
The 34-year-old American, who has never won on the PGA Tour, moved to the top of the leaderboard after a superb six-under 65 on Saturday put him two shots clear of compatriots George McNeill and Charlie Beljan.
Jason Allred and left-hander Brian Harman are a further shot back on a leaderboard dominated by home players.
McGirt burst out of the blocks with five birdies and a bogey in his opening six holes on the famous par 71.
Further birdies at 10 and 11 gave him a two-shot lead and he extended that to three with another from 10 feet at the par four 13th.
McGirt, who had missed the cut on his only two previous starts at Riviera, dropped a shot at 15 and looked set to ship another at the 18th after his drive leaked right and struck a cartpath.
However, his ball bounded so far down the concrete, it cleared the dogleg and allowed him to punch a seven-iron onto the green and two-putt for par.
"I'll take 65 any day, especially around this place. It's playing really well this week, the fairways have finally firmed up," said McGirt.
"I've never seen it this firm. I'm hitting a lot less clubs into a lot of holes which makes it a lot easier for me. I need it to play fast."
McNeill started his five-under 66 with an eagle at the par five opening hole while Beljan eagled the 11th in his 68 which also featured four birdies and two bogeys.
The biggest dangers may lie in the six-man group at eight-under. They include Masters winners Bubba Watson and Charles Schwartzel, last week's winner Jimmy Walker, rising star Jordan Spieth and Ryder Cup ace Dustin Johnson.
Watson made the biggest move on Saturday with a bogey-free seven-under 64.
Lee Westwood is the highest-placed European on six-under.
The Englishman made par at his first 11 holes but birdied 12, 13 and 17 for a three-under 68 which left him at six-under for the tournament.
US Open champion Justin Rose - playing his first tournament in 2014 after being sidelined with a shoulder injury - is nine shots off the pace despite his best round of the week so far, a three-under 68.