Avram Grant has slammed Chelsea for allowing Diego Costa to leave the club so easily in the January transfer window.
The Spanish international began the 2017-18 season with Chelsea, before being told he was surplus to requirements by Antonio Conte.
Costa sealed a £57m transfer to former club Atletico Madrid in January, and ex-Chelsea coach Avram Grant believes that the board should have tried harder to keep the 29-year-old forward.
"You should not release a striker like Diego Costa so easily and think that everything will be okay," Grant told reporters.
"Today the top teams do not release anybody. It is a new era because there is a lot of money in the game. It affects you.
"If you take Diego Costa away, you can see part of the reason why Chelsea has not been so successful this year."
Costa has scored four goals and assisted three since rejoining Atletico earlier this year.
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