World number one Dustin Johnson fired eight birdies in a seven-under par 64 on Friday to grab a share of the second-round lead alongside rookie Beau Hossler at the Pebble Beach National Pro-Am.
Johnson, playing on the par-71 Monterey Peninsula course, one of three in use for the tournament, had just one bogey as he gained ground on overnight co-leader Hossler.
Hossler, who played the par-72 Spyglass Hill, had five birdies in a five-under 67 that put him on 12-under as well.
The leading duo were two strokes in front of Julian Suri, who carded a four-under 67 at Monterey Peninsula to get to 10-under and Troy Merritt, who shot a five-under 67 at Spyglass Hill.
Five-time major-winner Phil Mickelson, a four-time winner in the tournament that teams amateurs from the world of big business, sports and celebrity with the pros, put himself in the mix for the weekend with a bogey-free 65 at Monterey Peninsula that left him tied for fifth on nine-under par.
"I am having fun," said the 47-year-old American, who is seeking a 43rd US PGA Tour title and his first since the 2013 British Open.
He hit nine of 13 fairways and 15 of 18 greens in regulation but said he expected a tougher challenge when he plays the par-72 Pebble Beach Golf Links on Saturday.
"I think Pebble's a little bit tougher because the greens are a little firmer and smaller," he said "But if you play well, you can birdie and score low on all three (courses)."
World number two Jon Rahm of Spain had five birdies without a bogey in his five-under par 67 at Pebble Beach on Friday. That put him alongside Mickelson in the group of six players sharing fifth place on nine-under, which also included former world number one Jason Day who posted a six-under 65 at Monterey Peninsula.
Northern Ireland star Rory McIlroy, playing the tournament for the first time, was five-under for the tournament through 13 holes of the second round when disaster struck at Monterey Peninsula's driveable par-four fifth -- his 14th hole of the day.
He nearly drove the green and putted his eagle attempt to within 10 feet. But he needed four more putts from there, recording a double-bogey on the hole. He added two more bogeys on the way to a three-over 74.
He was one-under for the tournament, with work to do on Saturday to make the 54-hole cut.