Foremost, the Marlins want the 25-year-old fully ready and not playing through any discomfort this spring.
Morrison is recovering from right knee surgery, and Thursday he began a rehab program where he ran on an anti-gravity treadmill.
In a few weeks to a month, Morrison will progress to running on the field.
Morrison acknowledged Thursday that being ready for Opening Day on April 1 at Washington is a long shot.
The first baseman hasn't ruled out playing sometime in April.
"Very possible," Morrison said. "I don't know exactly when in April, but I'm hoping it's before May."
It's been a rough last couple of years for Morrison, who has had two surgeries to his right knee.
A year ago, he pushed it in Spring Training, and it resulted in him getting off to a slow start. In 93 games a year ago, he batted .230 with 11 homers and 36 RBIs.
"You've got to be healthy in this game," manager Mike Redmond said. "It's hard to be banged up and injured. He's one of those guys that we've just got to take our time with him and ease him back into it, make sure that he's 100 percent healthy and 100 percent ready to go when he goes out there. We want to have him over the course of a season and not just a month or so."