Why has Diego Costa's relationship with Chelsea turned so sour?
When did this all start?
Costa signed for Chelsea from Atletico Madrid for £32million on a five-year contract in July 2014, but there have been continual reports of a move back to the Spanish capital ever since. Hamstring problems plagued his first season but the striker still scored 20 goals in Chelsea's 2014-15 title-winning campaign. There were also on-field disciplinary issues accompanied by retrospective suspensions which led Costa to consider leaving England. Some Chelsea supporters also blamed him for Jose Mourinho's departure in December 2015. He reestablished their faith and scored 20 goals in a second Premier League title success last season.
What about his relationship with Antonio Conte?
Costa was integral to Jose Mourinho's Chelsea, leading the forward line with a snarl as arch-antagonist and chief goalscorer. His importance was similar to Conte's Chelsea side last season, with some suggesting the Blues would not have won the title if they had let Costa leave in January. That was when the major fissures occurred as Costa was left out of the team for the win at Leicester following reports of a behind-the-scenes row over a mega-money move to China. Publicly Conte insisted it was because of a back injury.
If he was so important, why is he surplus to requirements at Chelsea?
Conte may have decided Costa was not worth the trouble. The celebrations after the title-clinching win at West Brom in May included Costa, perhaps jokingly, brandishing a fire extinguisher while Conte spoke to a group of journalists. It was a tiny snippet of what it might be like to manage Costa on a daily basis. Plus, if he has agitated for a move, the striker's loyalty may be in question. Costa is also 29 in October, so Conte may want a younger man to lead his team. He has now got Alvaro Morata.
Did Conte make the decision to get rid of Costa?
Yes - and this is where there is some dispute. Chelsea and Conte say Costa and his agent, Jorge Mendes, knew in January that the striker would be leaving this summer. Costa claims he was informed by text message in June and has engaged his lawyers. He was expected to return to London in the last two weeks, but remains in exile in Brazil saying Chelsea are fining him for not returning to the club. He is under contract for two more years, but the fact the row has become public - and Costa's determination to rejoin Atletico, rather than go elsewhere - significantly reduces his value.
What happens next?
There are a number of possible scenarios. Chelsea could agree a deal for Costa to join Atletico, who cannot register new players until January due to a transfer embargo, so they may loan him out elsewhere. With no deal with Atletico agreed, Costa could also remain in Brazil, effectively on strike while the lawyers continue to negotiate. Alternatively, Costa may return to London, training with the Chelsea reserves or on his own, winding down his contract and waiting for a transfer to Atletico. The most unlikely scenario would see a reconciliation with Conte and Chelsea, which would allow for Costa's return.