Justin Rose cruised into a three-shot lead at the halfway stage of the Farmer Insurance Open as overnight-leader Jon Rahm struggled on day two at Torrey Pines.
Rose continued the form he displayed in his opening 63 on the North Course, and he made light of the difficulty of the South layout on day two as he made seven birdies against just one bogey in a 66 that lifted him to 15-under par.
The world No 1 matched the earlier score of Hideki Matsuyama, who is Rose's closest challenger heading into the weekend, while Rory McIlroy hauled himself into contention with a 65 while Tiger Woods did just enough to survive the cut despite a frustrating 70.
Rose got off to an erratic start and found fairway bunkers at each of the first four par-fours, but a superb second from the sand to seven feet at the fourth would result in a birdie and he went even closer on the next, his approach from a trap on the left gripping and spinning to within three feet.
He made it three birdies in a row at the long sixth before tugging a wedge left of the target at the seventh and failing to save par, although Rose responded with a two-putt birdie from 15 feet at the ninth to turn in 33.
Rose was on the mark again with his new irons at the 10th as he set himself up a tap-in birdie and, after another four at the par-five 13th, he rolled in a 25-footer for a two at 16 and parred in to stay comfortably clear of Matsuyama.
The Japanese ace picked up two birdies and an eagle over his last five holes to claim the early clubhouse lead until he was surpassed by Rose, while Rahm and Billy Horschel faltered down the stretch to slip out of the tie at the top.
Rahm's all-round game led to the occasional fit of pique as the fiery Spaniard mixed two birdies with a pair of bogeys in a disappointing 72 that left him where he began the day, while Horschel dropped three strokes on the back nine on the South after racing into a share of the lead with five birdies in six holes.
Horschel's sparkling run included a monster putt for birdie from over 70 feet on the seventh, but he would go on to count the cost of missing fairways on the inward stretch, with back-to-back bogeys at 15 and 16 taking the gloss off his excellent start.
Rahm and Horschel share third with Ryan Palmer (67), while McIlroy hauled himself "right back in the tournament" with an entertaining 65 on the North Course that propelled him to eight under and seven adrift of his Ryder Cup team-mate.
McIlroy opened with an eagle from 20 feet on the 10th at the North layout, and he holed his second from the fairway at the 16th for an eagle-two before two-putting for his first birdie of the round at the next.
The Torrey Pines debutant also birdied two of his last three holes either side of his lone blemish of the day at the short eighth, and his closing four ensured he would finish the round in the top 10 and alongside Aussie veteran Adam Scott, who added a 66 to his opening 70.
Woods rued a series of missed opportunities on the greens for the second day running as his 70 on the North featured four birdies but also a double-bogey six at the 18th - his ninth - where he did well to gouge his ball out of a heavily-plugged lie in a greenside bunker.
Back-to-back birdies at three and four got him back inside the cut line, but he was unable to take advantage of the two remaining par-fives as the seven-time champion remained on four under and 11 strokes behind Rose.