The Blues' double Player of the Year recipient looks increasingly likely to be heading to pastures new, with David Moyes' Manchester United his reported destination.
Indeed, according to a tweet from Matt Law of the Daily Telegraph, Mata has "told family and friends he is joining Manchester United."
It's hard to understand why Jose Mourinho would even countenance the player's sale.
After all, it wasn't long ago when he was singing Mata's praises, per Sam Wallace of the Independent:
People love him, but also the fellow players love the work he did for the team. Of course, he fits in my plans.
I know him quite well. I have my idea about him. I have my idea about where and how he produces better, and where he has more difficulty.
But we are here to try and keep him performing when he is, and try and help him to perform better in the situations where he finds it a bit more difficult.
It was a fairly unequivocal statement, made at the beginning of the season—"Of course he fits in my plans."
Will Jose Mourinho regret selling Juan Mata?
So where did it all go wrong for Juan Mata? How is it that a player of such guile and craft has only made 12 appearances in all competitions under Mourinho (per whosocred.com)?
Of the 12, Mata has only played the full 90 minutes on four occasions, and one of those was against Swindon in the Capital One Cup. Hardly the sort of treatment someone of Mata's evident quality deserves.
I don't like the way Chelsea were playing the last couple of years; the club doesn't like it and we want to change. We want to play a different style. The past is history, even my past. I'm here like I've just arrived.
The way I'm reading the situation and the reasons why, in this moment, he's [Mata] not playing so much are things I can speak about with him, but not publicly.
It's part of a process with him, too. It is one thing to play with Ramires and Oscar closing down opponents on each side, and Mata as a No. 10 behind a striker with his clever assists, clever passes and fantastic actions because he has great talent.
But it is another thing to adapt to the way we want to play. In this moment, Oscar is my No. 10 and, if anyone tells me Oscar has not been Chelsea's best player this season, I'd have to disagree.
I have to prove to the fans that I am good. Now [Mata] must do the same, but only when [Mata] adapts to what we want.
Running great distances and closing down opponents have never been the Spaniard's forte anyway, and Mourinho's criticism of the player is at odds with his earlier fulsome praise.
In any event, despite not being the supreme athlete that Mourinho desires, there aren't too many better in the playmaker role in which Mata excels.
His style is pleasing to the eye and not forced, with a caress and ownership of the ball that is total. And he rarely wastes a pass.
An 88 percent completion rate across the season (per squawka.com) compares extremely favourably to other players in the position.
We should also keep in mind that before the Special One's triumphant homecoming, Mata had been an integral part of both the Champions League- and Europa League-winning sides.
Teams that played beautiful football, winning football.
Ex-Chelsea manager Ruud Gullit is another who can't understand Mourinho's standpoint, per SkySports:
He was one of the best players last year, therefore it's something personal.
I think they [Chelsea] can play much better football than they've shown. It's sometimes too tactical. With the players he has you don't need to be like that. You can be a little bit more adventurous.
He took that out by not playing Mata.
Whilst the deal is still to be done, everything points toward one of Stamford Bridge's finest making the move to Old Trafford.
It's a deal Jose Mourinho may live to regret.