Valencia and Villarreal are both under investigation over allegedly breaking FIFA rules regarding the transfers of underage players.
Rules prohibit players under the age of 18 from completing an international transfer unless it is between two EU nations or if both the player and club have their home or headquarters less than 50 kilometers from a national border.
Barcelona, Atletico Madrid and Real Madrid have all been hit with transfer bans in recent years for similar offences, although Los Blancos did get their punishment halves following an appeal.
Chelsea – who have been punished before – are also under investigation for breaking the rules, along with Manchester City and two unnamed Serie A clubs.
