Costa has started to say his farewells to his Chelsea team-mates with the Premier League champions facing the threat of suffering a striker crisis ahead of the new season.
Manchester United’s move for Chelsea’s top striker target Romelu Lukaku has left the London club in a difficult position, as they work to find out whether there is room to launch an 11th hour bid of their own.
Chelsea are yet to rule themselves out of the Lukaku race and have noted Everton’s denial that a deal with United is agreed. The Belgian had favoured a return to Stamford Bridge, which may yet be something Chelsea try to exploit.
Should they be forced to admit defeat, then Chelsea will have to switch targets and could renew their interest in Alvaro Morata, who they bid for last summer, or Alexis Sanchez, who Arsenal have insisted will not be sold to a Premier League rival. Torino’s Andrea Belotti is another option.
Chelsea head coach Antonio Conte is due to return to work on Sunday and was understood to be anxious about the club’s striker situation, even before United made their £75million bid for Lukaku.
His decision to tell Costa that he is no longer part of his plans by text message looks increasingly ill-advised and has complicated Chelsea’s transfer plans.
With Atletico set to make their opening bid to re-sign Costa, the Spain international has got in touch with a number of his Chelsea team-mates to tell them he expects to return to his former club and is unsure whether he will be back at Chelsea for pre-season training which starts next Monday.
Chelsea will only excuse Costa from returning for pre-season if a move to Atletico is agreed or negotiations are advanced, which the 28-year-old clearly hopes is the case.
It remains to be seen, however, whether Chelsea are forced to try to broker a truce between Conte and Costa if they fail to land Lukaku.
That seemed inconceivable a couple of weeks ago, but Chelsea may yet be forced to explore all their available options, including keeping Costa, if Lukaku completes a move to United.