The Argentine attacker is not yet recovered from the thigh injury he picked up against Atletico Madrid in the Spanish Super Cup and will miss this weekend's Liga encounter
The prolific attacker sustained a thigh problem in Wednesday's Supercopa de Espana game versus Atletico Madrid and was taken off at half-time due to the knock.
Messi underwent further examination on Thursday, revealing a bruising to his left thigh, and Martino has now revealed that he will consequently miss Sunday's match against Malaga.
"We are pretty optimistic about Messi's recovery. He's not in the squad as a precaution, because we don't want to take any risks at this stage of the season," the Barca coach stated at a press conference.
The 26-year-old netted twice in Barcelona's 7-0 victory over Levante in Barca's season opener, but will not be able to add to his tally at the weekend.
New signing Neymar is likely to make the starting XI for the first time in an official game following Messi's absence, with the Brazil international netting against Atletico after replacing the Argentine at half-time.