Morrison had surgery last September, and a more realistic return date could be mid-June.
"LoMo is going to start playing in extended spring training games on Tuesday. That's exciting," manager Mike Redmond said. "He's been running the bases. He's ready for game action. That's good. He hasn't played in a long time. He will be able to go out there and start getting some at-bats."
Catcher Jeff Mathis, on the DL with a broken right collarbone, will play one more rehab-assignment game with Class A Jupiter. Then, he will be moved to Double-A Jacksonville.
Right-hander Henderson Alvarez, who opened the season on the disabled list with right shoulder inflammation, played catch on Monday. Recently, Alvarez had a setback. He is starting now to build back up.
Giancarlo Stanton, out with a strained right hamstring, continues to rest and hasn't started any baseball-related activities.
Joe Frisaro is a reporter for MLB.com. He writes a blog, called The Fish Pond. Follow him on Twitter