Reports are suggesting the Blues are locked in negotiations with Manchester United over a potential £40 million deal to take the Spaniard to Old Trafford. And according to the Evening Standard, it's a move that will only happen if Mata puts in an official transfer request.
A similar tactic was used last summer by United when they refused to allow Wayne Rooney a move in the opposite direction.
Knowing the uproar the sale of such a vital player to their rivals would cause, David Moyes and the United board refused to budge on their stance unless Rooney attempted to push the transfer through himself.
He didn't and the Englishman very much remains a United player. Things may not be so simple for Mata.
How Chelsea's most recent Player of the Year has come to find himself in this position is no mystery but nevertheless remains the biggest surprise since Jose Mourinho returned to Stamford Bridge.
Mata has been an influential figure with the Blues since joining from Valencia in 2011, helping them to success in the Champions League, FA Cup and Europa League.
That doesn't cut it for Mourinho, however. He wants more from his players and right now he's getting it from Eden Hazard, Oscar and Willian, who occupy the three attacking positions in the Chelsea midfield.
What Mata gives Chelsea going forward, Mourinho feels he lacks defensively and as such, his team is a weaker prospect as a result. Put simply, the system and philosophy the Portuguese is attempting to install doesn't suit a man of Mata's ilk, hence his bit-part role throughout 2013-14.
Now it's crunch time.
While the transfer window remained closed, Mata couldn't do much else other than maintain a low profile and put the graft in on the training ground to show his manager he should be a part of this Chelsea team.
To his credit, he's done that. Mourinho has spoken in glowing terms of Mata's attitude and, despite plenty of opportunities, Mata hasn't fallen into the trap of publicly criticizing his manager.
His reputation has remained in tact, although as the end of January fast approaches, things are set to change.
He may have been frozen out by Mourinho, cast aside with the impression he is now surplus, yet when it comes to the Spaniard's future, Mourinho is leaving Mata to decide if his torment continues or not.
It's an unenviable position.
Should he remain in West London, Mata's hopes of featuring for Spain at this summer's World Cup will be all but dashed. He hasn't featured for Chelsea since being substituted against Southampton on New Year's Day, and the signs suggest he isn't going to be rushed back into the team any time soon.
If he puts in a transfer request and leaves to join United, however, Mata will be waving goodbye to everything he has achieved in the past two and a half years. All the affection Chelsea fans feel for him right now will be gone in an instant.
It's the clubs who will be winning—Chelsea receiving a considerable profit on the £23 million outlay they made for Mata, while United, despite the fee, are signing one of Europe's finest players who has the ability to turn their season around.
For Mata and Chelsea fans, it's a different outcome altogether. The player will be making a move he has never publicly shown an interest in, while the supporters lose a hero in the process.
Who could have predicted that when Mourinho waltzed back into Stamford Bridge?
Garry Hayes is Bleacher Report's lead Chelsea correspondent and will be following the club from a London base throughout the 2013-14 season. Follow him on Twitter @garryhayes.