Barcelona have called for clarity from FIFA after world football's governing body appeared to refuse permission to register Arda Turan in light of Rafinha's injury.
Turan joined Barca from Atletico Madrid during the close-season, although the Spanish and European champions are under a transfer ban for breaching rules relating to registering youth players.
Under the sanctions, the club are not allowed to field Turan until January 4, but Barca approached FIFA and the Spanish Football Federation (RFEF) after Rafinha suffered a cruciate knee ligament injury last week, ruling him out for several months.
FIFA has now stated that Turan cannot be registered early, although Barca want a clearer line amid suggestions they could take the case to the Court of Arbitration for Sport if the request is not granted.
A club statement released on Friday read: "FC Barcelona received a communication from FIFA in relation to the request for permission of the RFEF to register Arda Turan.
"FIFA's communication has not answered the request of FC Barcelona but merely states '"just for information" that in its opinion the RFEF is not allowed to register the player because its laws "could be in conflict" with FIFA's laws.
"FC Barcelona insists of FIFA the need of a more concrete answer, saying yes or no, because FC Barcelona is not asking an opinion, it is asking for permission or not, because the CAS ruling forbidding transfers during the two 2015 windows has already been served entirely as the club understands."
Aleix Vidal, who joined Barca from Sevilla in the close-season, is also prevented from representing his new club until January.
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