Messi has not played for Argentina since last year's World Cup last-16 elimination but the five-time Ballon d'Or winner is back for friendlies against Venezuela and Morocco.
Fresh off his 33rd LaLiga hat-trick, Messi will feature in the clash with Venezuela on Saturday (AEDT) in Madrid before facing Morocco four days later, and Udinese keeper Musso is relishing his return.
"We're very happy," Musso said. "He trains like the rest of us and for us it's an honour to have him back in the national team.
"I hope all of us can meet the expectations on us and get the results that we're looking for."
Messi – Argentina's all-time leading scorer with 65 goals – has scored a LaLiga-high 29 goals this season and 39 in all competitions for Barcelona.
The 31 year-old, who has netted six goals in his past three games, last scored for Argentina in their dramatic late win over Nigeria to advance to the round of 16 at Russia 2018.