Boca Juniors plan to start legal action following the early departure of midfielder Neri Cardozo to Mexican club Jaguares.
Cardozo cited a FIFA loophole when he left Boca six months before the end of his contract finishes to join up with former Boca boss Miguel Angel Brindisi at Jaguares last weekend.
Boca vice-president Jose Beraldi said: "The legal office of Boca Juniors know the procedures to follow and we should respect what they and the (South American Football) Confederation decide.
"The player has no extension. He has a running contract, and at the same time Boca have the right to use a one-year extension. You will have more details when the legal office make the official presentation of the report.
"We are not interested in the money but in the legal situation in order not to set any precedents and stop this situation that is difficult in football.
"Boca will call Cardozo for the pre-season. But we are aware of the situation, and the attitude of the player and his agent shocked us."
Players' union spokesman Sergio Marchi told Ole newspaper that Cardozo "has the right to terminate his contract."
He explained: "It has nothing to do with the type of contracts players sign in Argentina, nor extensions. It is happening all over the world.
"If both clubs do not agree any compensation, Boca will not send the international transfer. Then FIFA and the CAS (the Court of Arbitration for Sport) will start working to let him play."