Despite having only two birdie chances inside 15 feet, Mickelson holed out from the eighth fairway for eagle and chipped in for birdie on the par-3 16th.
That carried him to 1-under-par 70 and a one-shot lead over Pat Perez in the Northern Trust Open.
Mickelson made three par saves from outside 10 feet, starting with his opening hole at the par-4 10th. He went from the front bunker to the back bunker, blasted out safely to 18 feet and curled in the par putt.
That set the tone for a day that only looked good on the scorecard.
“I probably didn’t play the greatest today, but I was able to kind of salvage a good round and had a good break on eight where I holed out from the fairway,” he said. “That was a nice little bonus.”
Perez equaled the tournament best of 65, without a bogey on his card, and he saved his best shot for the final hole. He hit his tee shot on the 18th and was too far right, the green blocked by the eucalyptus trees. Perez cut a 6-iron, hopeful of finding the green, and it wound up 12 feet away for a birdie he wasn’t expecting.
“I didn’t hit it like you’d think I would,” Perez said. “I didn’t drive it all that great. I just scrambled well. I put myself in the right places to make par or birdie.”
Mickelson was at 6-under 136, assured of being atop the leaderboard for the third consecutive round.
The group at 4-under 138 included Jimmy Walker (66), Carl Pettersson (70), Jonathan Byrd (70), Marc Leishman (69) and Matt Kuchar (69), who had a solid day without too much excitement until he drilled his tee shot to a back left pin on No. 6 and left himself 5 feet for birdie.
Before he could putt, he was stung by a bee in his arm.
Bubba Watson had 69 and was in the group another shot back, while world No. 1 Luke Donald had 72 and was only six shots out of the lead.
As usual, the 144-man could not finish before dark. Eight players will have to return this morning to finish, with the cut likely to be at 3-over 145.
Mickelson and Perez will be in the final group.