I am surprised at how many people are surprised with Mourinho's dislike for Mata. Mourinho doesn't like midfielders like that; instead, Mourinho prefers midfielders who fight hard and are successful on the defensive end, not just on the offensive end. Also, Lampard and Mata didn't play all that well together last year, and Mourinho loves Lampard and is known to be loyal to the players with whom he established connections in the past.
So, I wouldn't be surprised one bit if Chelsea sold Mata. Now, do we need him? Nope, not at all. He is too similar of a player to the ones we already have in the squad. Also, he is most effective when the ball is played through him at all times and I just don't see him and Silva on the pitch at the same time, whatsoever. Buying Mata would be a complete waste of resources. Better invest in CB.