The Argentina international has not featured for the club since suffering a hamstring problem in November's 4-1 win over Real Betis.
Having return to training on Thursday, following a period of recuperation in Argentina, Martino stopped short of setting a target date for his return.
"He's just came back to work with the squad, he trained on Thursday and played yesterday in the open training session so it is just a question of carrying on with his work," he said.
"We are talking to him every day to see how he feels and obviously he is closer (each day) to coming back and playing again."
Martino, whose side return to action after the winter break against Elche on Sunday, is also calm over slotting Messi back into his starting XI.
The 51-year-old claims Messi is regaining his "killer" instinct in training and is not worried about picking up further injuries.
"Everyone knows the kind of squad we have here at Barcelona, (and) for coaches, having more players available is never a problem and players understand the importance each one has," he added.
"I saw it in today's training, (Messi) is very keen. You can't make a mistake as a coach and expect too much but I see Leo really looking forward to playing again.
"He is looking good physically and has a killer's look in his eye.
"From the way I've seen him, there does not seem to be any fear when he has been playing."
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