How have Chelsea managed to make such a mess of the Diego Costa situation?
There were rumours that the player would leave the club midway back in January, amidst interest from the Chinese club Tianjin Ouanjian and a resulting row with Antonio Conte. Chelsea eventually kept hold of him, which was the right decision in terms of securing the Premier League title, but was bound to make things tricky in the future.
The standard of football in the Chinese Super League is still well below that in Europe's top leagues. Costa may well have agreed to a lucrative move to China when the clock was ticking in January and he'd fallen out with his manager, but given the benefit of time was always likely to consider alternative options.
Judging by his Instagram page it seems that Costa has decided that a return to Atletico Madrid should be the next step in his colourful career. Costa posted a video of himself last night wearing an Atletico shirt and responded to a comment from his Chelsea colleague Cesc Fabregas with the reply, 'Give Conte a hug'.
No one should feel sorry for Conte because he's also guilty of having been rash with his mobile phone this summer. At the end of last season he sent a text message to Costa to bluntly point out that the striker was no longer part of his first-team plans.
For a manager who dealt so well with the politics at Stamford Bridge in his debut campaign, that decision was shockingly naive. A selling club needs buyers to know that they're perfectly willing to retain a player in order to extort maximum transfer value, rather like Everton did so successfully with Romelu Lukaku.
Oh yes, Lukaku... The Belgian was widely expected to join Chelsea as Costa's replacement, only for Manchester United to make the first and ultimately decisive move. Chelsea came in with a late bid, but by then the player had made up his mind. Let's not forget also that Lukaku is someone that Chelsea already had on their books, before selling him three seasons ago for far less than the £75m they were willing to pay to bring him back to the club.
We all know that financial common sense is not such an important factor at Chelsea as it is at other clubs. Even so, the club's upper management are likely to be kicking themselves, having created a situation that could prove very costly, on and off the pitch.
Costa is agitating for a move to Atletico Madrid, who are banned from buying players until January. They are still willing to make a move for Costa this summer and let him sit out until 2018, but you can bet that absence will be factored into the price they're willing to pay.
Meanwhile, Chelsea need to find a replacement for Costa, having let one slip through their fingers twice. Alvaro Morata has been mentioned as a possibility, but now looks likely to join AC Milan. Pierre-Emerick Aubameyang, Andrea Belotti and Gonzalo Higuain are alternative options.
Whoever eventually replaces Costa is likely to be hugely expensive, as everyone knows how desperate a position they've put themselves in. Chelsea have just gone away on tour without Costa, leaving Michy Batshuayi - who scored five league goals last season - as their only striker.
Even if they do buy a proven international forward, there's no guarantee that they will be as successful as Costa. After all, Andriy Shevchenko and Fernando Torres were both considered the finished article when they joined Chelsea, but were spectacular failures. Costa may not be a truly prolific goalscorer, but his work-rate, strength and ability to bring others into the game, will be hard to find in another player.
Such uncertainty explains why Chelsea have drifted out to [5.3] to retain their Premier League title next season, having been backed as low as [4.0]. In a summer when Manchester City and Manchester United have already considerable strengthened, right now Chelsea are looking weaker than last season, with only 20 days remaining before the next campaign kicks off with the Community Shield match against Arsenal.