Diego Costa facing legal action from Chelsea if he does not return for training

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.

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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.

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 a deal 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 Stamford Bridge.

Chelsea dismissed Cardoso’s claim that Costa has been forced out by text message as “nonsense”, insisting the player and his advisors were told in January that he would be able to find a new team this summer

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 so far refused to meet Chelsea’s asking price for Costa, with the Spanish club also reluctant to pay his full £150,000-a-week wages until January, and his value will only diminish further the longer he remains in Brazil.

Chelsea are adamant they will not let Costa go for a knockdown fee, but, in theory, the club could investigate trying to sue the player and his advisors for the difference between his sale price and market value if it was felt he eventually left at a reduced price.

The Premier League champions are not currently looking at taking any legal action of their own and parallels have been drawn between the Costa case and Carlos Tevez going on strike in 2011 while he was a Manchester City player.

Tevez was reintegrated into the City squad after spending more than three months on strike in Argentina, during which time legal action was threatened from both sides.

The striker considered trying to sue then City manager Roberto Mancini, while City looked at the possibility of claiming compensation against Tevez for the reduction in his value.

Tevez eventually returned to City, apologised and remained at the club for over a year before joining Juventus where Conte was then manager.

Meanwhile, Leicester City are ready to tell Chelsea that they will have to hand over the Nemanja Matic money to land Danny Drinkwater in the final weeks of the transfer window.

Chelsea will make a second offer of around £25million for Drinkwater after having an initial £15m bid rejected by the Foxes.

Drinkwater is interested in a move to Stamford Bridge, but Leicester value the £27-year-old at £40m – the same fee Chelsea received for Matic from Manchester United.

Conte is desperate for new signings to be made following Chelsea’s opening day defeat to Burnley. But Southampton remain insistent that central defender Virgil van Dijk is not for sale and sources close to Alex Sandro do not expect Juventus to sell the left-back at this stage of the transfer window.

Other than Van Dijk, Chelsea are interested in Southampton right-back Cedric Soares and have also looked at Paris Saint-Germain’s Serge Aurier.