By Mark Lamport-Stokes
The American world number two, the top draw at Torrey Pines this week in the conspicuous absence of top-ranked Tiger Woods, bogeyed the first three holes in the final round on the way to an untidy one-over-par 73.
Mickelson covered the back nine on the South Course in one under to end up in 19th place, five shots behind winner Ben Crane, and felt his overall game was better than his scoring reflected.
"I had a good warm-up session and I felt like it was going to be a good day," the 39-year-old told reporters. "I got off to a terrible start and then throughout the round didn't get much out of it.
"But the good thing is that I've got a direction of what I'm working on. I hit some good shots coming down the stretch. The last 13 or 14 holes I actually hit a lot of good shots.
"I've had some success up at LA so I'm excited about next week."
Mickelson began the final round at Torrey Pines four strokes off the pace but he lost ground quickly with an outward nine of two-over 38.
"It happens," the three-times major winner said after totaling 32 putts in the round. "I felt I was ready, though. I was really excited about playing. Maybe I was a little over-anxious.
"My timing was off a little bit this week and today's putts didn't quite go in the hole, even though they were catching the edges most of the time."
"I wasn't able to accelerate through the ball very well and I was hanging back a little bit. At least I know what it is that I need to work on and I have a couple days to do it."
The Northern Trust Open will take place from February 4-7.
(Editing by John O'Brien)