Annoying thing about the Mkhitaryan situation is you know once Mou eases him in he's going to be a fixture in the 11. I do agree with the rational though, I think Jose wants to slide him into a functioning team. He's bigger and faster than Mata so I can see why he'd be preferred on the RW there where he's going to be expected to push on past Zlatan. That said, Mata is clearly working really hard, his pressing and closing down game is light years ahead of where it was under LVG, as his goal against Bournmouth showed. He's never going to be a physical threat but I can't fault his work rate at present.
With Pogba in the side now, I feel Mata has more of a chance, our team is actually pretty beast physically. I disagree with Jam about the reason for height, I think its more a defensive issue than a attacking reason, but we can nearly put out a 6ft+ team. Once we get the defensive positioning sorted, with a keeper like DDG guarding against long shots, if we want to close out a game not that many side will feel optimistic swing balls into a box with Bailly, Smalling, Pogba, Fellaini, and DDG in goal.