If you've ever wondered why controversial but highly prolific striker Diego Costa no longer features for the Blues, here's a recent revelation by the man himself.
Diego Costa has described his treatment by Chelsea like that of a "criminal" and confirmed he wants to join Atletico Madrid.
The striker, 28, last played for Chelsea in the FA Cup final in May, and was sent a text in June by boss Antonio Conte telling him he would not be part of the squad for next season.
Costa says the club are now demanding he return to train with the reserves.
"Why won't they let me go if they don't want me?" he told the Daily Mail.
"I have to do what I have to do. I have to think of myself. I've been a good boy here and tried to do the right thing. My desire is to go to Atletico."
Costa joined Chelsea from Atletico Madrid in 2014 and has won two Premier League titles and the League Cup with the London club.
In January, he was left out of the Chelsea side for an away match at Leicester after he was involved in a dispute with a fitness coach.
It followed reports of an offer from China that would have been worth £30m a year in salary.
"In January, things happened with the coach," said Costa. "I was on the brink of renewing my contract and they put the brakes on it. I suspect the manager was behind it. He asked for that to happen.
"His ideas are very fixed and clear. I have seen the sort of person he is. He has his own opinion and that will not change.
"I respect him as a great coach. He has done a good job and I can see that, but as a person, no. He is not a coach who is very close with his players. He is very distant. He doesn't possess charisma."
In June, Costa said Conte sent him a text telling him he would not be part of the squad for next season.
"I have not deleted the message," he added. "If people accuse me of lying, I can show them. It was clear, saying that he didn't count on me and wishing me the best for the future. Full stop."
The Spain striker was given extra time off by Chelsea last month, but now claims he is being fined for his absence and is considering legal action or seeing out the remaining year of his contract unpaid in his native Brazil.
"You know that the manager doesn't want me," added Costa.
"I am waiting for Chelsea to set me free. I didn't want to leave. I was happy. When the manager does not want you, you have to go."