The Spaniard arrived at Old Trafford from Chelsea in January, and the £37.1m fee was the most new United boss David Moyes had shelled out for a player, and the former Valencia star was seen as one of the first pieces of the anticipated revolution from Moyes.
But some of the doubters had pointed out a big flaw in the plan. Mata predominantly played as a #10 at Chelsea, meaning he would slot in behind the striker and create between the lines - something that most teams would love to have.
Yet the problem for United was that they already had a player in that position - Wayne Rooney. The England international has had a turbulent couple of years at Old Trafford, but has recently signed a new contract, suggesting Moyes sees him as an integral part of the team - leaving Mata to play out on the flanks.
As predicted, Mata hasn't been at his best having been shoved out wide, and the 25-year-old has stated that he isn't comfortable playing out wide, and would rather be in the centre of United's three-ponged attacking midfield alignment.
"Right now I am playing on the right but to honest I don't see myself as a proper winger," Mata said. "I love to play between the lines as a No.10, come inside, that is where I feel comfortable to play; to keep in touch with the ball because I love to play in possession and with the ball."
With Rooney unable to really play as a lone striker or out wide, Moyes may have a problem pleasing everybody - which is something many had envisaged when news broke of Mata's impending arrival. The possible departure of Robin van Persie could ease matters, but even then there is likely to be a 'square pegs in round holes' scenario developing at United.
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