Avram Grant believes Chelsea made a mistake by letting Diego Costa go
Former Chelsea coach thinks it might have cost the Blues this season.
"You should not release a striker like Diego Costa so easily and think that everything will be okay.
"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."