However, he also acknowledges that the 17-year-old will need support in Madrid to reach his full potential.
Scaloni made these comments ahead of Argentina's World Cup qualifier against Colombia.
"Going to Real Madrid is a huge opportunity," Scaloni said. "We are talking about one of the best clubs in the world."
Scaloni believes that Mastantuono's determination, mentality, and desire to learn will serve him well at Real Madrid.
However, he also emphasized that Mastantuono is still just 17 years old and will need guidance and support to continue improving.
Scaloni expressed his happiness if Mastantuono joins Real Madrid, as it would demonstrate that big clubs are taking notice of Argentine football.
He mentioned that other Argentine players, such as Javier Saviola, Juan Roman Riquelme, and Pablo Aimar, have had successful careers in top European leagues.
Real Madrid are reportedly in advanced talks to sign Mastantuono for his €45m buyout clause, with the youngster set to remain with River Plate for the rest of the year.