London: 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 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 will be agreed. The Spanish side’s transfer embargo, which runs until January, has complicated the matter, although Deportivo La Coruna and Real Betis have indicated they would be willing to take Costa on loan until January.

However, the striker has so far rejected the idea of a temporary move.

Costa revealed that he has been fined for failing to return to Stamford Bridge.

In an interview this week, Costa claimed he was prepared to stay in Brazil and keep being fined for the entire season if Chelsea do not agree to sell him to Atletico.

Costa’s lawyer, Ricardo Cardoso, has also warned that he “will use all possible legal mechanisms” to allow his client to leave his current employers.

Chelsea say that any legal consequences of Costa’s situation are hypothetical and remain adamant that he must return to training and work to make himself available for selection.

Should he fail to do so, however, Costa and his representatives could face the threat of being sued for effectively wiping millions of pounds off his valuation.

Atletico have refused to meet Chelsea’s price for Costa and are reluctant to pay his full 150,000-pounds-a-week wages until January, and his value will only diminish the longer he remains in Brazil.

Meanwhile, Leicester City are ready to tell Chelsea that they must pay 40 million pounds for midfielder Danny Drinkwater — the same fee the Blues received from Manchester United for Nemanja Matic.