Troublesome Chelsea striker Diego Costa may well throw another spanner in Chelsea’s works, according to the latest reports from Spain. Premier League Champion leading scorer wants to move back to his former side Atletico Madrid, while his old club is trying to persuade him to force a return to the Spanish capital. Also, Read; Report: Chelsea told to pay £90m for Torino strikerThe 28-year-old Costa has already agreed to terms with his former club, for whom he banging in 43 goals in 94 Liga games where he won La Liga with Madrid base side. The Spanish international striker is threatening to refuse to train if the Premier League Champion Chelsea won’t let him move back to Spain. Chelsea forward who recently revealed that he wants to play, preferably for his former club. The scorer of 22 goals last season in all competitions for the Blues, he was dumped at the end of the season by the Italian boss Antonio Conte via Whatsapp. Costa had tried to force a move away during the winter to money bag China, but leading to a bust-up with the Blues manager Conte. He is expected back on Monday but could sit out pre-season training in order to force a move away. Chelsea has refused the Liga side’s £26.5million offer recently, as they believe their striker is worth a whole lot more.