"I'm hoping I'm definitely rehabbing in April," he said on Tuesday morning. "I'm hoping that the beginning of May, I'm back in a big league game."
Mathis, who turns 30 on March 31, was hurt in Miami's first Grapefruit League game. His collarbone was broken on a foul tip off the bat of St. Louis' Matt Holliday.
An X-ray taken on Feb. 23 showed the break. Saturday will be one month since the incident. On Friday, Mathis will be examined by Dr. Frank Cook, the team physician, and another X-ray will be taken.
"We'll get another picture taken, and we'll go from there," the veteran catcher said. "I've already started moving it, trying to get back some mobility."
Mathis is moving gingerly. He refrains from any movements above his right shoulder and he uses his left hand to greet people, opting not to shake with his right hand.
"I'm moving it a little bit better," Mathis said. "I'm able to grab some things and do some things. As far as up over my shoulder, I'm not there yet. Everything [below the shoulder], I've had some progress."
The Marlins acquired Mathis from the Blue Jays in November.
An eight-year MLB veteran, Mathis broke in with the Angels in 2005, and he spent 2012 with Toronto.
Mathis entered Spring Training as Rob Brantly's backup.
If the Marlins don't seek options outside of the organization, Kyle Skipworth is considered the front-runner to be Miami's Opening Day backup catcher.
Missing a month of Spring Training has been a frustrating experience for Mathis.
"It's starting wear on me a little bit," Mathis said. "I've been around, but not having a schedule. I've got nowhere to be, except for therapy for an hour, and some cardio stuff, as much as I can. I miss being out there on that field."