The five-time Balon D'Or winner will start in La Albiceleste's clash with their old enemy Brazil in Melbourne on Friday night.
The match will mark Sampaoli's first game in charge of the team, and the former Sevilla boss has commended Messi for his commitment to his country.
"I've found a player that has a lot of desire to play for the national team," Sampaoli said. "He is a reference.
"I had talks with him that allowed me to know that he is deeply committed for Argentina to reach the World Cup.
"Leo is very simple, humble and a good teammate. He is very positive. As a football leader he can help a lot."