Mastantuono has long been on the radar of Los Blancos, who have somewhat monopolised the South American market in the last seven years to scout and snap the biggest talents emerging from the continent.
Multiple reports from Spain confirmed last year that the club already had a verbal agreement in place with River Plate, with only the financial details left to be finalised. However, those talks seem to have stalled, at least for now, given that Mastantuono is just 17 years old. With his contract expiring on December 31, 2026, a big move to one of Europe's big clubs seems inevitable.