Diego Costa could face the threat of being sued by Chelsea if he ignores the club’s requests to return to training.

And the saga could yet extend past the end of this month, as Atletico Madrid can sign Costa after the transfer window has closed on the understanding he would not be able to play until January.

Chelsea have once again ordered Costa back from Brazil, where he has spent the entire summer hoping that a return to Atletico Madrid will be agreed.

Atletico’s transfer embargo that runs until January has complicated the matter, although the Spanish club can sign Costa after the window has closed on the agreement he cannot be registered to play until the New Year.

FIFA will allow clubs to sign a contract with a player in or outside a transfer window, as long as the rest of their regulations are adhered to.

Deportivo La Coruna and Real Betis are the latest clubs to indicate they would be willing to Costa on loan until January, but the striker has so far rejected the idea of a temporary move before re-joining Atletico.

Costa revealed that he has been fined for failing to return to Chelsea since receiving Antonio Conte’s text message informing him he was not part of his plans for this season.