Martino says "from what I see (Messi) is excited to play, he is fit, with the eyes of a killer," but he still "lacks playing time."
Messi trained with his teammates this week for the first time since tearing his left hamstring in November, having spent time in Argentina doing rehab.
While Messi continues to improve his fitness, goalkeeper Victor Valdes made the squad for Sunday's game against Elche. Valdes hasn't played for six weeks since injuring a right leg muscle.
Xavi Hernandez is also back from injury, while Dani Alves is out with a fever.