Why have LaLiga prevented Barcelona from registering Gavi and Ronald Arajo as first-team players?

Gavi could be described as the ultimate midfield player, which youll be able to see for yourself in Barcelonas Copa del Rey quarter-final against Real Sociedad on Wednesday. He has shown terrier-like tenacity from the moment he burst onto the scene at the age of 17, coupled with a huge amount of technical ability, which has always been present but has perhaps shone through even more of late now that he seems to have learned to control his aggression. The teenager has become a regular in the Spain midfield and started 18 matches for his club this season yet LaLiga still wont let Barcelona register him as a first-team player

Why cant Barcelona register Gavi and Ronald Arajo as first-team players?

The 18-year-old signed a new contract with La Azulgrana in September which stipulated that he was a member of their first-team roster, which the club had hoped would be enough to meet the leagues registration criteria. However, new regulations mean that Bara have no financial margin to register any new players due to the fact that their wage bill far exceeds the salary cap that LaLiga have established. And thats despite the sale of Memphis Depay to Atltico Madrid and Gerard Piqu's retirement in November.