Messi, 31, is set to make his international return after missing his nation's matches since last year's World Cup in Russia.
But Menotti, who coached Argentina to World Cup success in 1978 and is now the country's director of national teams, is worried about Messi's wellbeing.
"I'm afraid that Messi plays," he told FM 94.7.
"I see him with important emotional fatigue between the Champions League and the national team. I see him very tired.
"If he wants to play with Argentina, better."
Argentina will face Venezuela on Friday before taking on Morocco four days later.
Tottenham boss Mauricio Pochettino has aired his belief Barcelona are favourites to win the Champions League in large part due to the Catalan side having the "best in the world" in Messi.
“If there's a favourite to win the Champions League, it's Barcelona,” the Spurs boss said.
“They have players at a very high level, like Leo Messi, who is a genius and the best in the world.
“Barcelona have excellent, extraordinary footballers, but they also have someone in Messi who is a genius, someone even more different, extraordinary and unique.
“Leo does things that nobody expects, but what continues to surprise me about him is his consistency. He's being doing it with regularity, every three or four days, for the last 11 or 12 years.”