The stayaway Spain striker has been given an ultimatum by the Stamford Bridge club to return to this country, start training, get himself fit – and make himself available for selection.
Costa has been absent from training at Chelsea for four weeks and has been fined £300,000 by the club after failing to return to pre-season training, after being given an extra week off.
Costa gave an interview earlier this week saying that he is “not a criminal” and did not deserve to be treated as one by Chelsea.
He said that he was prepared to spend a year at home in Brazil if necessary without playing, if it meant eventually forcing a move to Atletico Madrid, the club he is determined to join.
But last night the club hit back hard, as they ordered the Spaniard back in uncompromising terms, to fulfil the terms of his £150,000 a week contract.
Talks have taken place between Chelsea and Atletico over a move for the 28 year old, but the Spanish club are under a Fifa ban from signing players until January.
Until an agreement can be reached with the Spanish club, Chelsea are adamant that Costa fulfils the terms of his contract, which runs out in June 2019.
Chelsea manager Antonio Conte sent Costa a text message at the end of last season telling the striker that he had no future at the club.
It remains highly unlikely that Costa will ever play for Conte again.
However the club are concerned that in his current state of fitness – the 28 year old has been pictured drinking in bars and larking around on the beach back home in Brazil in recent weeks – they will not be able to sell him, or loan him before a move to Atletico to anyone.
Chelsea have also contested Costa’s claims that he is being forced to train with the reserves. But he will continue to be fined for every week that he remains absent from the club, breaching their code of conduct.
Costa’s lawyer Ricardo Cardoso last month threatened legal action over Chelsea’s handling of the player and threatened to use “all possible legal mechanisms” to force a return to Atletico.
The Spanish club have already seen a bid of around £26million for Costa rejected by Chelsea, who are determined not to allow last season’s top scorer to leave for a bargain price. Chelsea though want around £40million for the striker, who scored 22 goals for the club last season.
He said at the weekend: “I am waiting for Chelsea to set me free. Why won’t they let me go if they don’t want me? My desire is to go to Atletico. I’ve spoken to Chelsea director Marina Granovskaia. I said, ‘If the manager doesn’t want me, I want to go to Atletico Madrid’.
“They want me to be there training with the reserves. I wouldn’t be allowed access to the first-team dressing room and I would have no contact at all with the guys.
“I’m not a criminal! I don’t think it is fair after all I have done to be treated like that.”
Chelsea, meanwhile, are closing in on a £35million deal for Arsenal’s England midfielder Alex Oxlade-Chamberlain, with talks ongoing between the two clubs.
Conte’s side disastrously lost their opening game of the season on Saturday 3-2 at home to Burnley, and the Italian once again reiterated that he needs new players. The Blues are also set to up their bid for Leicester midfielder Danny Drinkwater to £25million.