Just five months ago, the thought of writing such an opening sentence would have seemed utterly preposterous.
After all, Mata was arguably Chelsea’s most accomplished player, who looked set to play a leading role under Jose Mourinho's new regime.
Since arriving from Valencia in the summer of 2011, the Spanish international had become a Stamford Bridge favourite for his flair, quick feet and important goals and assists.
He had been voted Chelsea’s Player of the Year in both of his first two seasons as he helped the club win the Champions League, the Europa League and FA Cup.
Mata is only 25 years old, so still maturing and several years from reaching his peak.
Surely Chelsea couldn’t possibly contemplate selling their best player to the reigning champions, however wounded they would become under David Moyes this season?
And yet Mata is now a Manchester United player: How did this happen? How did it evolve from a rumour to a done deal?
Chelsea confirmed their interest in Rooney with a formal bid but denied they would allow Mata or Luiz to move in the other direction.
Despite the denial, those two names were now in the public domain and it planted the seed of doubt in their minds as they began to ask themselves: Am I still wanted?
By the end of August, it was clear to Mata he was no longer wanted by Mourinho.
As The Guardian reported, it was at the end of August as the summer transfer window closed that Manchester United first began to learn that Mata was not wanted by Chelsea and could be interested in a move to Old Trafford.
As moves for Cesc Fabregas and Ander Herrera ultimately failed, United didn’t immediately act on this information about Mata but rather decided to monitor the situation.
What they saw was Mata increasingly being left out of the team by Mourinho and go from star player to peripheral figure.
The Spaniard was not prepared to sit on the sidelines, especially as it was potentially harming his chances of being in his country’s World Cup squad.
As reported by The Guardian, Mata sought an agreement with the Chelsea hierarchy that if he was not being played, then he could be sold in the January window.
Chelsea agreed to his request and put a figure of €45m on his head. They also decreed he could not be sold to Manchester United; however, Mata later had this condition removed.
United were made aware of this agreement and the player’s desire to join them if he continued to be ostracised by Mourinho.
When the January transfer window opened, United did not immediately pounce, appreciating Mata would not be allowed to join them until they had played Chelsea at Stamford Bridge on January 19.
According to The Daily Mail, on Thursday last week Manchester United sent Chelsea a written bid for €45m for Mata.
The United hierarchy preferred this old-fashioned means of communication to avoid Chelsea seeking to include Wayne Rooney in the deal. United would not countenance selling their striker.
It is curious United seemingly could not trust themselves to simply resist Chelsea in any phone conversations or face-to-face meetings; however, it did prove to be a successful approach.
The next day Jose Mourinho spoke about Mata’s sale in his press conference as if it had already happened.
However, the deal wasn’t concluded until the following day when the Spanish international travelled to Manchester, completed his medical and signed his contract.
After the rumours had first surfaced, it had taken only six months for Mata to become a United player.
In fact, it was a relatively courteous transaction for all parties, as the player didn’t aggressively agitate for a move and there was little rancour between the buying and selling clubs.
Now that the deal has been done, it remains to be seen whether Mata can revive United's season and whether Mourinho can demonstrate he was right to cash in on the player.