GK's using wrong squad numbers

Just as a pointer. When I say that 'only goalkeepers can use 1, 13 and 25', I mean not only that a outfield player cannot use it, but most importantly: that the goalkeepers cannot use anything other than those.

Hello, is there an official source stating this that you could link us too?

Hello, on the Spanish Football Federation (RFEF) official website:

https://rfef.es/sites/default/files/images19/001_primera_y_segunda_division.pdf

On page 5. Direct translation:

Cita

The numbers of the footballers will be between the numbers 1 and 25,
reserving 1 and 13 for the goalkeepers. Given the possibility of a
eventual third goalkeeper, licensed in the first team, will be reserved
the number 25. 

Regarding the #25, this means that in real world a outfield player could use 25. But I don't know if this can be reflected in FM, so I think the best way is to directly reserve those 3 numbers for the goalkeepers, to avoid confusion and bugs. 

The reality is that in 23/24 season, there are only 3 outfield players, in Spanish First Division, who wear #25. Teams usually reserve that number in case they need to sign another goalkeeper.

Thank you for the information.