Chelsea striker Diego Costa blasted over ‘unprofessional’ conduct by Bryan Robson

CHELSEA striker Diego Costa is acting unprofessionally by staying away from the club, says Manchester United legend Bryan Robson.

Diego CostaGETTY

Chelsea striker Diego Costa wants to join Atletico Madrid

Costa has refused to return to Chelsea training after being told he will be sold this summer.

In a statement from his native Brazil today he confirmed he wants to join Atletico Madrid.

"My destination is already made,” Costa said, via his hometown club Sportivo Sergipe.

“I must return to Atletico Madrid. It turns out that there is the impasse that Chelsea does not want to release me.

“But I believe that this situation will be resolved now on my return to Spain.”

Chelsea have already fined Costa £300,000 for not showing up to work.

And United legend Robson says the striker’s behaviour is wrong.

“What I’ve got to say straight off is that it’s so unprofessional,” Robson said on talkSPORT.

“If you’re a player and you have a contract and have signed with that football club you have got to honour that contract.

Bryan RobsonGETTY

Manchester United legend Bryan Robson (right) has hit out at Costa's behaviour

Ray Wilkins believes Chelsea could take Diego Costa to court

“You signed it, you’re getting paid really well. The club have had great success. It’s totally down to the player.

“He should be much more professional and should come back and honour his contract.

“If Chelsea want to keep him that’s what he has to do.”

Chelsea have already signed Alvaro Morata from Real Madrid as a replacement for Costa.

The Blues are hoping to earn as much as £50million for the two-time title winner.

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