Open champion Mickelson was fighting his swing throughout his round and finished with a one-under 71 to sit tied 21st.
The big lefthander registered two double bogeys, one at the ninth when he hit his tee shirt into the water, and said only his putting saved him.
"I can't remember swinging this bad in a long time, and as I shoot video of my swing I'm doing everything wrong," Mickelson said after his opening round of the 2013-14 PGA Tour season.
"The path of the club is too inside, then it's vertical, the head's moving, my legs are loose. Divots are steep. It's terrible. This is the worst I've hit and I can't find the middle of the club face.
"And I'm not sure if the ball is going to go dead left or snap hook right and it's a frustrating time tee to green. But I'm putting okay."