The two-time major winner has not played since pulling out of The Players Championship in mid-March after one hole due to back spasms. He then withdrew from last week's Masters tune-up in San Antonio with a back injury.
"The honest truth is I'm taking it day by day," Morikawa told reporters at Augusta National. "It's not exactly where I want to be, and it's unfortunate, but that's just the body, and I can't push it.
"It's been a little bit of a mental battle, I think, just trying to trust with where it's at. The back actually feels fine. It's just other parts of the body not cooperating a little bit how I want."
A seven-time winner on the PGA Tour, Morikawa has been hitting balls for the past week but does not yet have the comfort level he would like going into the year's first major and said there are some shots he cannot hit given his physical and mental restrictions.
"It's a work in progress. But each day just staying positive, trying to get through it," said Morikawa.
He spent part of Monday playing a nine-hole practice round alongside four-time major champion Scottie Scheffler and world number three Cameron Young.
Morikawa, who earlier this year won the AT&T Pebble Beach Pro-Am and finished fifth in the Arnold Palmer Invitational, is looking to make his seventh Masters start this week at Augusta National, where he has finished inside the top 20 in each of the past five years.
"It's frustrating, but at the same time, I can't do anything stupid and push my body in a way it doesn't want to do," said Morikawa.
"What's amazing is chipping and putting still feel great. The putter feels amazing. Just got to be able to get the ball there, which is like the opposite of how I've been, I think, my entire career."
