Chelsea and Diego Costa could be heading for the courts.

The Express says the Premier League champions are understood to be considering suing the rebel striker for up to £50 million if he continues to refuse to return to the club.

They would claim breach of a contract from which Costa is paid £185,000 a week - the club's second highest earner - and which still has two years to run.

Costa, who has been named in Chelsea's 25-man Premier League squad but not in their Champions League one, is now also understood to be consulting his lawyers.

The Brazilian born star's bitter battle with Chelsea and coach Antonio Conte turned distinctly uglier last night after he failed to get the move to Atletico Madrid he wanted when the Spanish transfer window closed yesterday.