Even if you don't think he should be a starter... why should we sell a player who is never injured, never complains and will - at the very least - be a great squad option to have... especially since we have an incredibly thin squad as it is, and half of this thin squad spends the majority of its time on the treatment table - except Mata. Whilst I get that some people don't like Mata, the idea of demanding him be sold is completely irrational when looking at our current squad.
Also, Van Gaal is holding us back, not Mata.
Never complains? he has a face like a smacked arse every time he is taken off or is on the bench. I don't see him as a great squad player.. at the moment he is pretty much a starter in 9/10 games and therefore he hasn't thrown his toys out of the pram. Under someone competent like Jose, he'd barely get a look in and I can't see him accepting such a role.
He also has a fair amount of value attached to him, we could recoup a fair bit from selling him (maybe in the region of £25-£30m).
I wouldn't sell him until replacements are brought in first. It is irrational to sell players and then completely flop in terms of bringing in replacements.. lets nail some transfer targets first and then we can balance the books by letting him go.
Van Gaal of course has held us back but I can't help but feel that he has suffered greatly due to decisions taken by Moyes and he has exacerbated the situation by not rectifying these mistakes. The signing of Mata, Fellaini and the contract extension of Rooney was three of the most catastrophic decisions taken by United in the past 4 years and the main reason why we are the cumbersome mess we see today.
Whenever Van Gaal has been forced to play youngsters/quicker players.. his philosophy doesn't look all that shite and we look half decent on the ball.
Ultimately he himself is responsible but Mata/Fellaini and Rooney will epitomise this era for me.. Cannot wait for the day when all three of them as well as the manager are not at this club.