Messi recently made his return to the national team having stepped away in the months following the 2018 World Cup.
At that World Cup, Argentina were heavily-criticised as the team largely underperformed under Jorge Sampaoli, crashing out in the last 16 against eventual winners France.
But Mascherano says Messi deserves credit, not blame, for the efforts he has put in with Argentina.
"They always look for something to criticise him for. They said 'he has to return', and when he gets back, he's the problem. He's always the problem," he told TyC Sports.
"I'm not in his shoes, but I can imagine he should be tired. The criticism is not about the game.
"They talked about how he dismissed himself after the Venezuela game, but they didn't say anything about how he trained with the team for 10 days before the matches against Spain and Italy [in March 2018, before the World Cup] when he knew he wouldn't be able to play.
"Do you know how many times he travelled to the USA, prior to some friendly game, knowing that he would not play, just to be with the team?"
Mascherano went on to discuss the team's ill-fated 2018 World Cup run, one plagued by rumours of a dressing room revolt against Sampaoli.
But they lasted just one more match before falling 4-3 at the hands of France in the first knockout round.
"Against Nigeria, we reached an agreement with Sampaoli, to solve some doubts that we were having on the pitch," he said.
"He was always the manager. He made the decisions and decided the team. We spoke about everything with him.
"Sampaoli selected the team for the match against France. When you try to deny spaces on the wings, Mbappe will kill you.
"The plan was to defend on our side of the pitch and try to counterattack. Clearly, it didn't work."