Retegui chose the Azzurri having never played in the country as he was born and raised in Argentina.
Father Carlos Retegui told TMW: "The most important thing is that the national team does well, the goal is the result of teamwork, and it is always a goal for everyone. Mateo feels very appreciated by coach (Luciano) Spalletti, he is very grateful to everyone.
"It is a source of pride for him to play with the Italian national team, it is an eternal glory to wear the blue."
On leaving Genoa this summer for La Dea, Retegui Snr also said: "Mateo is very happy at Atalanta. He was also happy at Genoa, for which we have only words of thanks. Today he has found a super-organized club, with a coach who has a lot of passion and wisdom like (Gian Piero) Gasperini.
"He must continue to learn every day, work hard to offer the best version of himself, second by second, minute by minute, always thinking about improving for the good of the team. My son is truly happy at Atalanta."