The Special One was right to put Mata in his place after a disastrous day for the Spaniard's future with the club and his relationship with the esteemed manager.
Mata was substituted out of Chelsea's Jan. 1 match at Southampton, despite it being a scoreless game and in the 53rd minute. Needless to say, Mata wasn't pleased, as he ignored Mourinho while walking past him and wore his frustration on his sleeve after joining his team-mates on the bench.
Here's a short video that includes some of Mata's displeasure:
As you would imagine from a respected manager such as Mourinho, he took exception to Mata's frustrated actions. While not saying so directly, he hinted that nobody will stop Mata from leaving Chelsea if he chooses to do so, per Daily Mail's Neil Ashton.
Mourinho, clearly aware of his player's unhappiness, said: ‘I don’t want him to go, that is my opinion and that is my wish—but my door is open.
The club door is open too, so when a player wants to speak with us we are there waiting for them. But if you ask me do I want to sell him, I don’t want to.'
This could be overlooked if it were just any other player. But it's Juan Mata, and that makes it carry much more significance.
Mata has been voted the club's most valuable player twice and is a star midfielder of the future for Spain's national team. It took £23.5 million to get him to Stamford Bridge—a value that could rise even higher for the 25-year-old.
His value has been undeniable to Chelsea. Before Mourinho arrived, that is. Since then, there's been some sort of issue with him in the starting line-up as he's only started and finished two Premier League games.
For perspective, he started and finished 13 league games a season ago, and hardly was an unused substitute—a status he's unfortunately seen six times already this season.
Mata has shown in his first two seasons in London that he can be one of the Premier League's best midfielders, but for whatever reason, he hasn't quite meshed with the transition to the Mourinho era.
No player can be perceived as above the team, and that's especially the case in a place like Chelsea where control at the top was in flux for years before Mourinho returned. His arrival brought a lot more order to the squad and different expectations.
Clearly, Mata is not living up to whatever expectations Mourinho has of him. With Mata being the subject of Inter transfer rumours, per the Mirror's Darren Lewis, this distraction needs to get itself figured out one way or another before the January transfer window ends.
Plus, Mourinho has all of the control. His Blues are playing awfully well, and Mata is hardly making an impact on the club even though they're two points from the top of the table.
Maybe this whole deal will light a fire under Mata and bring out his best form. Maybe his relationship with Mourinho will be fixed behind closed doors and he'll slowly emerge as the player he was prior to this season. Maybe a dose of "we don't need you" will help his drive and to buy in to the system a bit more.
But that's all Mourinho can hope for at this point. Considering the distraction that would become of one of his best players pouting openly on a regular basis, he needs to figure out as quickly as possible whether Mata wants his future to be in Chelsea blue or not.