Jordan Spieth charged into the halfway lead at the Farmers Insurance Open after firing a stunning second-round 63 at Torrey Pines.
The in-form youngster took advantage of playing the easier North Course as he carded a flawless nine-birdie round to snatch the lead from Stewart Cink, while Tiger Woods finished a frustrating day nine shots off the pace.
Spieth opened with a birdie at the 10th and picked up further shots at 13, 14 and 18 before maintaining his momentum on the front nine.
The 20-year-old American reeled off another five birdies in seven holes from the second to hit the front on 10 under, while overnight leader Cink returned a one-under 71 on the South Course to earn outright second.
"I've been feeling great since I got here," Spieth told www.pgatour.com. "I'm striking the ball really well."
Spieth was playing in a group alongside world No 1 and defending champion Woods, who is bidding for a remarkable ninth victory at the California venue in his first start of the year.
Woods also started with a birdie, but he picked up only one further stroke at 15 before closing with a scrappy six at the long ninth to post a 71 and make the halfway cut with just a shot to spare on one under.
"I wouldn't say my game is rusty," he said. "It was just a fraction off and, you know, at this level and on golf courses like this, if you're just a fraction off it doesn't take much."
Former Open champion Cink birdied his last hole to sneak a shot ahead of Ryder Cup star Nicolas Colsaerts, whose blemish-free 67 was the best round of the day over the South Course.
"I think it suits my game pretty good," the Belgian told Sky Sports 4. "It's a long ball-park. If you get the right shots into greens (it is a) US Open-type set-up. I like it."
Australian Marc Leishman and American Billy Horschel shared fourth-place on seven under, while Scotsman Russell Knox is among a group of five players a stroke further adrift.
Lee Westwood and Keegan Bradley were amongst those at three under while Phil Mickelson withdrew from the tournament after struggling to a one-over 73 to close on two under.
The Open champion is struggling with a back muscle problem, and he made the decision to pull out after seeking medical advice.