It does. Right now Di Maria is the man in form, but Mata himself is evidence that these things can change very quickly. One year ago today the argument would have been in Mata's favour. Di Maria's position at Madrid was looking uneasy and Mata had just come off a sensational season at Chelsea. Things changed, Mata was a victim of Mourinho's changes and Ancelotti came across a formation that suited Di Maria down to the ground.
I don't know if he will be the one to suffer. In truth, neither do you. He could fall by the wayside but I think that would be wrong. That would be the third good player between the 23-27 age bracket we'd have cast aside in a matter of months, in favour of stroking the egos of near 30 year olds that have all sorts of question marks surrounding their fitness and form.
Like you say, we should be playing two - or three, I think is possible - of Mata, Rooney, Van Persie and Falcao. For me, Van Persie should be the first fall guy. The oldest, the least dynamic and the most likely to succumb to injury. I'm worried this won't be the case.