The potential sale of Juan Mata for a reported £40 million from Chelsea to Manchester United is shocking. It breaks two unwritten rules in football transfer dealings, and could be made by a manager in Jose Mourinho who doesn’t make transfer errors very often.

The two unwritten rules are:

1-      Never sell a player to a rival club,

2-      Never sell a player of Mata’s quality in January if you are in a title race

Jose Mourinho may be thinking tactically short-term though. Title rivals Arsenal and Manchester City still must face Manchester United in the league this season while Chelsea do not face the reigning champions again. Potentially strengthening United at this point when the margin is so thin between the top three clubs in the league is a tactical move by Mourinho.

Certainly the sale of Mata to a rival club does not make much long-term sense for Chelsea as he could provide the impetus for a revival by Manchester United in time for next season’s title race. Two seasons ago, Chelsea discarded Yossi Benayoun — deeming him surplus to requirement — spent a season on loan at Arsenal. Towards the end of the season with both the Gunners and Chelsea fighting for a Champions League spot, Benayoun played a key role in several Arsenal victories. The Gunners finished 3rd while the Blues finished 6th, only achieving Champions League football thanks to the dramatic victory in Munich.

While Chelsea did not pay for the foolishness of loaning Benayoun to a rival club, they should have been considering they ended up finishing three places behind Arsenal in the table. It was the type of mistake  I assumed Chelsea would not repeat. In the case of Mata, it is unlikely to hurt them this season, but if they sell him outright to Manchester United, it could very well harm them in the longer term.

For Manchester United, this potential deal makes plenty of sense. Sure £40 million would top the transfer record for any non-London club in English football, but Mata is desperate to play in order to claim a spot on Spain’s World Cup team. Furthermore, United is full of bad vibes and negativity right now. Much like the arrival of Mesut Özil lifted the sagging spirit among Arsenal supporters, Mata’s arrival is likely to do the same for United.

In addition, acquiring Mata will make it easier to part with Wayne Rooney if the Englishman continues to avoid signing a new contract with the club. Rooney is one of the world’s finest footballers when fit, but in between his spells of petulance, injuries and his advancing age, Mata’s addition will make it much easier to sell him on.

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