The Barca midfielder has tipped his compatriot to fire Alejandro Sabella's men to victory, beginning with their friendly against Germany on Wednesday
Messi has been shortlisted among the top three candidates to win the Uefa Best Player in Europe award, and Mascherano is confident his countryman holds the key to inspiring their side to winning the 2014 World Cup.
"Inside us, we all think of Messi as our leader," the former Liverpool midfielder quipped to Argentine publication Clarin. "Who else could it be, but the best player in the world?"
"Coach Alejandro Sabella believes we are capable of inflicting more damage to our opponents, certainly greater than the amount we can suffer. We are capable of fielding four players who are very direct at any time, including [Angel] Di Maria.
"Given the selections available to Germany at the moment, however, they must be one of the best teams, certainly only behind Spain. The match will prove to be an important test."
The World Cup 2010 semi-finalists host Messi and co in Frankfurt at 19:45 CET.