Real Madrid paid around €50m for Mastantuono last summer following his move from River Plate, but the winger failed to meet expectations in his first season in Spain and the club now believe a temporary departure is the best route for his continued development.
Fulham, managed by former Real Madrid defender Alvaro Arbeloa, have registered concrete interest, with the connection between the pair dating back to Arbeloa's time overseeing Mastantuono during the 2025-26 season, when the 18-year-old featured in 18 matches under his guidance.
At just 18, turning 19 in August, Mastantuono could move to Craven Cottage with the aim of gaining experience in one of the most competitive leagues in Europe, away from the pressure that comes with representing Real Madrid, and under a coach who already knows and trusts him. It would represent a similar path to that taken by several past Real Madrid academy products sent out on loan to develop, including Dani Carvajal, Fede Valverde and Fran Garcia.
Mastantuono is currently training with the first team under new head coach Jose Mourinho and started in a pre-season friendly win over Alcorcon on Friday, though he was not on the pitch for the winning goal, scored by Yanez after the senior players had been substituted off.
He was involved in the game's biggest moment of the first half, drawing a clear penalty inside the opening minute that Arda Guler saw saved by the goalkeeper. Despite his active display, the general view at Valdebebas remains that a loan exit is the preferred option for the coming season, with Fulham positioning themselves as the strongest candidate to help the Argentine rediscover the form that made him such a highly rated talent at River Plate, though the west London club are likely to face competition from elsewhere in Europe before any deal can be finalised.