(CNN) -- Colombian Camillo Villegas carded a two-under-par 70 to lead American John Rollings by one stroke after the second round of the Buick Invitational event at Torrey Pines, San Diego.
Villegas continues to set the pace after carding a two-under-par 70 at the Buick Invitational.
A winner of two events last year, including the Tour Championship, Villegas moved to 11-under-par 133 after 36 holes, despite not hitting the heights of his nine-under-par opening round 63.
Rollins charged up the leaderboard with a brilliant eight-under-par 64, although a final hole bogey prevented him from going into the final two rounds joint top with Villegas.
Villegas had extended his overnight lead to six strokes midway through the second round, but Rollins roared into contention with a sensational final nine holes.
Rollins, who started his round on the 10th hole, made up six shots in an eight-hole span on the front side, including a birdie-eagle-birdie spree from numbers four to six.
Bidding for his first title since the 2006 BC Open, Rollins pulled into a tie with Villegas after a birdie at the par-three eighth. With a chance to grab the outright lead at the par-five ninth, Rollins drove into the rough and hit his third shot into a greenside bunker, forcing him to settle for a bogey and sole possession of second place -- three ahead of Charley Hoffman.
Hoffman also made a late run with birdies on three of the final five holes en route to a six-under 66. He is four shots back and alone in third place at 137.
Paul Goydos (66) and Nick Watney (69) are tied for fourth place on six-under 138, while England's Luke Donald (69) heads a cluster of five players at 139.
Aaron Baddeley and Davis Love, who started the day two shots off the pace, both struggled and fell back in the pack. Baddeley had five bogeys and a double-bogey to fall nine shots off the lead, while Love (77) had six bogeys to drop 10 behind.
Phil Mickelson, who has won this event three times, had a roller-coaster round with four birdies and four bogeys in his even-par 72 to leave him on two-under for the tournament.
Meanwhile, British Open and PGA champion Padraig Harrington bogeyed two of his first four holes and never got back on track.
Harrington, who is playing in his first tournament of the season after having two non-malignant melanomas removed from near his right eye, carded a 74 to fall 12 shots off the pace.