Jose Mourinho knows what he is doing. That much is clear to anyone who knows anything about football. He has been doubted, his decisions scrutinised and his tactics dismissed time and time again but Mourinho has always prevailed and can be considered the best manager in the world at the moment.

When the sale of Juan Mata was agreed to by The Special One, many Chelsea fans were left distraught and many Manchester United fans relished the thought of unpacking their late Christmas present and showing him off to the world.

It seems incredible that Mata would make the move to Manchester after becoming twice Player of the Year at Chelsea since moving from Valencia in 2011. He became an immensely popular person in the changing room and after his debut goal against Norwich, he became a fans' favourite too. Mata was the lynchpin of the Chelsea team in previous years and was the player everyone looked to when something magical needed to happen.

This was all before the return of Mourinho. Upon his return, Mourinho placed his faith in Oscar as the number ten in the team. Nobody could understand why Mata was being cast off to one side when he was considered the best player at Chelsea. It was clear that while Mata was injured, Mourinho wanted to get rid of the dependency of the other players on the Spaniard.

He wanted it to be a team effort. He instilled the willingness to close-down and track-back in the Chelsea squad but whilst Oscar and Hazard obliged, Mata found this transition into a hard-working midfielder difficult. For that reason, he was often overlooked and when he did get the chance, he failed to leave a mark.

Slowly but surely, Mata became less and less important and soon became a "bench-warmer" hoping for a glimpse of the action in the final 15 minutes of the game. Unfortunately for him, Mata is not an impact player.

He is not someone like Willian, who will come on, harass the defence and run at a player. He is someone who dictates play from a central role. This only really works when you start - you cannot come on in the 80th minute and try to slowly build an attack. You need to hassle, run and inject life into the last minutes whilst gunning for the deciding goal. For all his obvious talent and ability - this is not Juan Mata.

Mourinho could not start him because Oscar was simply becoming undroppable and he could not introduce him because he would not have the desired impact. The only appearances became Capital One Cup matches and the final minutes in games that were already won. For this reason, Mata became, in Mourinho's mind, a pointless player and he was deemed disposable.

Whilst Chelsea fans could come to grips with selling their beloved Juan Mata, many wondered why he could not have been shipped off abroad to a team like PSG or Napoli - both of which were reportedly interested. Why did it have to be United?

The answer in the short term is that, seeing as Chelsea and Manchester United have already played twice in the league this season and United are not considered title contenders, it was never going to come back to haunt Chelsea. In fact, chances are that Mata could help United steal some points off genuine title rivals such as Manchester City and Arsenal. For this season at least, Mata could still indirectly be playing for Chelsea.

In the long term, Mourinho will be hoping that after handing Mata over to United, Moyes will return the favour in the form of Wayne Rooney in the next transfer window. Mourinho has been a firm admirer of the Englishman and will do anything to secure that he leads the line in blue next season.

It will take some getting used to to see Mata in the red of Manchester United but Chelsea fans must trust that Mourinho knows what he is doing. Mata's replacement, Salah, is someone who is more in the Mourinho-mould and will be able to impact games from the bench.

At the same time, people saying that Mourinho is too willing to sell good players must ask themselves a question: If Moyes had wanted Oscar instead of Mata, what do you think Mourinho would have said?

Chelsea have lost a good player and United have a gained a good player but if you take a step back and observe the situation from a neutral point of view it makes interesting viewing.

Moyes broke Manchester United's transfer record for a Chelsea substitute who could not get in to the team due to his inability to adapt, and plays in the same position as Wayne Rooney, United's best player this season.

Mourinho is undoubtedly the winner and Moyes will realise that throwing £40m at a luxury player is not what will get United out of their slump and in to the top four.

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Juan Mata