The joint overnight leader after producing an eight-under par 63 on Friday, Mickelson shot an even par 71 in the third round on Saturday thanks to birdies at the final two holes.
With his wayward work from the tees, Mickelson's round could easily have unravelled.
After going into the trees on the ninth, he went wildly right on the 10th and bogeyed before failing to find the fairway on his next three holes.
But, as he so often does, the world number three scrambled for par on all of them.
"I could easily have shot myself out of the tournament," he told reporters. "I shot even par today. I got it in the hazard I don't know how many times.
"If I go on and play the way I believe I'm going to this weekend I'm going to look back at those nine holes as the key to the entire tournament."
On the 14th, he finally found the fairway but then blasted his second shot into the rough and then he was in the water on the par-three 16th, where he made double bogey.
Then came two birdies to save his round and leave him still only five shots behind leader Sergio Garcia.
"That was one of my best numbers right there, because I was playing terrible and I shot even par," he said. "I fought hard. Throughout the course of my career, it happens, where you kind of lose it a little bit.
"I fought hard in the interim and was able to find it there in the end to give me confidence heading into the weekend but more than that, it kept me within striking distance."
The moment that summed up Mickelson's performance came on the par-three 11th, where a wayward shot from the tee ended up in some nasty rough behind the green.
His high shot landed two feet from the pin for a tap-in par after the lefthander produced a remarkable amount of back spin.
"I've not seen anybody else hit that shot, to be able to spin it back from that distance and lob it. It sure looks good," he said.
Adding to the spectacle, Mickelson was playing with Tiger Woods, who acknowledged his old rival's response to his troubles.
"That's what he does," said Woods. "It was pretty impressive to see the up‑and‑downs he made throughout that stretch, and holed a few putts, kept his round together."
(Editing by Nick Mulvenney)
