Franco Mastantuono has sparked a regulatory debate at Real Madrid after being registered with the club's Castilla team while making his first-team debut against Osasuna. The young Argentine, who arrived from River Plate in a €62.7 million deal, specifically requested to keep wearing the number 30 jersey he sported at his former club.

"I wanted to maintain this number because it has sentimental value for me from my time at River Plate," Mastantuono explained during his presentation at the Spanish giants.

The registration maneuver has drawn criticism from some quarters, with Miguel Galán, president of CENAFE, suggesting it could potentially constitute a "fraudulent alignment" under Article 125 of the Spanish Football Federation (RFEF) regulations. This rule prohibits using affiliate team relationships to circumvent the spirit of registration rules.

Interestingly, what Real Madrid has done with Mastantuono is actually common practice throughout La Liga. Over the past two seasons, more than ten players have regularly featured for first teams while being officially registered with reserve squads.

Betis utilized this approach with Chadi Riad and Sergi Altimira, while Sevilla did the same with Lucien Agoumé and Hannibal Mejbri. Even Las Palmas registered key players Fábio Silva and Dário Essugo with their B team despite their prominent first-team roles.

The practice offers clubs flexibility in managing squad registration limits and financial fair play restrictions. By registering players with their reserve teams, clubs can free up professional roster spots while still integrating young talents into the first team.

Despite the controversy, the regulatory framework actually supports this approach. Players under 23 registered with a reserve team can freely alternate between the reserve and first teams without limitation, provided they have a valid license and aren't serving suspensions.

By the way, none of these similar cases has ever resulted in sanctions from the RFEF, suggesting the practice is firmly within the boundaries of Spanish football regulations.

Will this controversy affect Mastantuono's integration into Xabi Alonso's squad? For now, it seems the young Argentine will continue wearing his cherished number 30 while training and playing with the first team – just like many other young talents across La Liga.