Charlie Wi carded a three-under 69 on stroke lead after two rounds of the Am.
Wi, who was one of three first-round leaders, finished 36 holes at 12-under- par 130. Having played Monterey Peninsula and Pebble Beach in the first two rounds, Wi will move to Spyglass Hill for round three.
With the pro-am format, the entire field rotates through the three courses for the first three days, then will shift to Pebble Beach for the final round.
Two-time winner Dustin Johnson, who shared the first-round lead with Wi and Danny Lee, managed an even-par 72 at Spyglass to fall into second place at minus-nine.
Vijay Singh, the 2004 champion, posted his second straight four-under 68 on Friday to move into a tie for third place at minus-eight. He was joined there by Padraig Harrington (66), Lee (73), Brian Gay (65) and Brendon Todd (69).
Phil Mickelson, a three-time winner of this event, shot five-under 65 at Monterey and headlines a group of nine players tied for eighth at minus-seven.
Tiger Woods, who is playing this event for the first time since 2002, managed a two-under 68 at Monterey to finish two rounds at minus-six. He is tied for 17th with Ryan Moore, Ricky Barnes and Richard H. Lee.
Woods got off to a quick start with a birdie on the first. However, he gave that stroke back with a bogey on the par-four fourth. Woods two-putted for birdie on the par-five sixth and followed with an 18-foot birdie effort on the seventh.
After four straight pars around the turn, Woods stuffed his third shot within two feet at the 12th. He kicked that in for birdie to move to seven-under, where he was five behind Wi.
Woods saved par from eight feet out on the 15th, but was unable to save par on 16. He parred the last two holes to finish at six-under.
"It was decent. I drove it good again today, unfortunately I just didn't make enough birdies," Woods said in a televised interview. "I was hitting the ball in the wrong spots, leaving myself sliders. I had to leave myself in better spots and didn't."
Wi started on the back nine Friday and stumbled to a bogey on the 12th. He quickly erased that error with a hole-out eagle on the par-four 13th. Wi moved to 11-under with a birdie on the 15th.
At the 17th, Wi faltered to another bogey, but atoned for that mistake with a birdie at 18 to claim a share of the lead.
Around the turn, Wi parred the first three holes before taking a one-shot lead over Johnson with a birdie on the fourth. Wi dropped another shot on the fifth when he failed to get up and down.
The 40-year-old Wi again bounced back with a two-putt birdie on the par-five sixth to move two clear of Johnson and Ken Duke, who bogeyed three straight holes after getting to minus-10.
Wi rolled in a five-footer for birdie on the eighth, but faltered to a closing bogey on the par-four ninth.
"I was very fortunate to make a two on 13 today. It got me off to a good start," Wi said. "The conditions were really tough with the greens being pretty firm, which we're not used to here at Pebble. The last four or five holes the fog rolled in and they played pretty long."
Johnson started with four straight pars from the 10th at Spyglass. After a birdie on 14, he bogeyed the 15th. Johnson converted birdie efforts on 17 and 18 to make the turn at 11-under.
The 2009 and 2010 champion dropped strokes on three and five. Johnson came back with a birdie on the seventh, but ended his round with another bogey on the ninth.
NOTES: Wi is winless on the PGA Tour, but does have four second-place finishes...Steve Elkington and Sunghoon Kang both withdrew on Friday...The cut will be made after the third round and will likely fall at one- or two-under par.