Even after starting with a 68, Mickelson felt he was close to putting his game together. It started with a 3-iron to 12 feet on the par-5 first for a simple birdie, and built momentum with a 60-foot birdie on the fifth and never slowed.
When he finished his best score ever at Riviera, he was at 10-under 132 and in firm command going into the weekend.
"This is a tournament that has eluded me," Mickelson said of the only city in the West Coast Swing where he hasn't won. "The West Coast means a lot to me."
Robert Allenby, who won at Riviera in 2001 in the cold and rain, did OK in warm sunshine with a 66 that put him at 136 with Jeff Quinney, who made bogey on the final hole for a 67.
Mickelson and the top dozen players atop the leaderboard got one big break with the draw by playing early Thursday and in the afternoon Friday, essentially avoiding the strongest of the wind that gusted along the eucalyptus trees lining the fairways.
For those who faced a cold wind Thursday afternoon and more swirling breezes Friday morning, the best anyone could muster was David Toms (68) and Kevin Sutherland (69), each at 3-under 139.
"It was interesting, the last 27 holes that I've played with the wind and everything," Toms said. "You certainly had to think about it on your club selection. It made a lot of the holes play very difficult. Overall, I'll take the two rounds I've put on the board."
For the second straight day, not everyone finished the round.
"So there will be a Saturday cut," quipped Rory Sabbatini on his way to the 18th tee as the sun began to dip behind the hill, and players were still just making the turn.
The Players Advisory Council recommended another change in policy to a Saturday cut if the field is more than 78 players. If approved, that wouldn't happen until Florida at the earliest. Otherwise, when the cut is more than 78 players, only the closest to 60 can play on the weekend, and the notorious "Rule 78" looked as though it could happen for the third time in five events.
The cut won't be made until six players finish the second round Saturday morning.
Scott McCarron, a UCLA alum who nearly won this tournament in 2002, had a 65 and was part of a large group at 5-under 137 that included Scott Verplank, Chad Campbell and Vaughn Taylor.
Mickelson wasn't about to practice posing with the trophy, and no one was conceding anything with 36 holes left to play on a course that was playing fast with the firm conditions.
"If Phil is at 10 under, that's fine," Allenby said. "There's a long way to go. There's still 36 holes to go and a lot of birdies out there. I've made plenty of birdies here before, so there's no reason why I can't do it on the weekend."
Quinney will join Mickelson and Allenby in the final group. Quinney made a late surge up the leaderboard, including birdies on the 12th and 15th hole, but ran into trouble on the last hole.