Gary Woodland forged one shot clear at the top of a tight leaderboard in the third round of the Farmers Insurance Open, while Tiger Woods crashed out of the tournament with an ugly 79.
American Woodland fired a two-under par round of 70 to move to eight-under 208 for the tournament, one shot clear of countryman Jordan Spieth and Australian Marc Leishman.
Overnight leader Spieth, who shot a scintillating 63 on the North Course in round two, found the tougher South Course a different animal with a 75 while Leishman ground out a 72 to be at seven-under.
Americans Pat Perez (72) and Morgan Hoffman (72) are tied for fourth at six-under while South African Rory Sabbatini (69), Japan's Ryo Ishikawa (69) and Americans Will MacKenzie (70) and Scott Stallings (72) are among those tied for sixth a shot further back.
"I played beautifully today. I drove the ball well, really controlled the golf ball into the greens, which is huge," Woodland said.
"The rough is up, the greens are firm and fast, so it was nice to drive the ball in play and give myself a lot of chances."
Defending champion Woods plunged to new depths when he missed a secondary cut on the PGA Tour for the first time.
Though he made the second-round cut by a stroke on Friday after carding a one-under-par 71 on the easier North Course, the world number one was badly out of sorts on a difficult day for scoring as he laboured to a 79 on the brutal South layout.
Playing the back nine first, Woods sat one-under on his round through his first eight holes before imploding.
He made back-to-back double bogeys on the 18th and first holes and then added five straight bogeys for a nine-over stretch of seven holes.
A birdie on the seventh and a chip-in par on the eighth brought a wry smile to his face before he parred the final hole to avoid shooting his first score of 80 or worse in the United States as a professional.
It was still his worst ever score at the event, which he has won a record seven times, and ensured he missed the third-round cut for the leading 70 players and ties.
Woodland rolled along in the opposite direction, with four birdies in his opening 14 holes catapulting him to 10-under and a three-shot cushion at the top.
He traded a bogey on the 15th with a birdie on the 16th but a costly double on his penultimate hole bit heavily into his advantage and left 22 players within four strokes of the lead.
"My putting was a little off today, I left myself a lot of testers out there, but I made some early and unfortunately I gave some back at the end," said Woodland, who is searching for his third win on tour.
"I have a game plan and my job is to execute. The people around me, we put a game plan together and we're playing very aggressive this week and all I have to do is execute.
"There's nothing different about Saturday morning or Sunday morning, I have to go out and play a good round of golf and hopefully it's enough on Sunday."
Spieth, 20, came back to the field quickly with two bogeys and a double bogey in his first five holes but battled hard from there to remain on track to be the youngest two-time winner on the Tour since 1932.
If he can come out on top on Sunday he will enter the top 10 in the world and beat Woods' mark to two wins by 21 days.
He would also beat Phil Mickelson's record as the youngest winner in the event by more than two years.
Texan Spieth grabbed birdies on the sixth and 11th holes, was rattled once more by back-to-back bogeys on 12 and 13, but birdied 15 to ensure the reigning rookie of the year remained well and truly in the mix.
"Only one shot back and a bunched up leaderboard, it's going to take a good score tomorrow," Spieth said.
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