Mickelson edged out Lee Westwood to win the Masters in 2010
Masters champion Phil Mickelson reacted to his worst result in seven months by changing his build up to Augusta.
The world number six, who has not won an event since the Masters last April, finished 55th at the WGC Cadillac Championship on Sunday.
He reponded by adding the Arnold Palmer Invitational to his schedule and could also play the Houston Open before the Masters on 7-10 April.
"I need more competitive golf - I've got some work to do," Mickelson said.
The American's preparation for last year's Masters had looked less than ideal, having failed to win for five months before picking up his third green jacket.
But after left-hander Mickelson closed with a 76 to end four over in Florida at the weekend, he decided to step up his preparation with three weeks to go until the opening major of the season.
"If I'd had a little more success earlier I probably would have not played Bay Hill," Mickelson added.
"I'm not shooting the scores I need to shoot. I'm not concerned with the way I'm hitting it or any particular element of my game, but I'm not shooting the scores."
Meanwhile, fellow former world number one Tiger Woods finished 10th in Florida.
"Every tournament that I've played this year I've felt better coming out of it - even though the results have not been good," said Woods, who has fallen to world number five after a run of poor form.
"I hit a lot of good golf shots and when I did mis-hit one I knew what the fix was right away.
"The driver is still not quite there, but I'm hitting it flush again, so that's just a matter of time before that comes around."