This was your original point. As i said, him not being good at tracking back is a myth. If it wasnt, you could easily point to times where this has happened and cost us / or weve conceded when his man has been free.
Much like im saying, "Im pretty sure United have conceded goals when hes come off (or been sacrificed) cos of the fact that one part of his game, which is under-rated, then goes missing." - where I can note two obvious examples against big teams where hes been subbed off, (Arsenal and Chelsea) which has lead to United not having / keeping the ball as much in the opponents half / having somebody to relieve us off that.
As I said, Mata has something not a lot of our players can provide against the bigger teams, and thats the part of him getting the ball and keeping it.
Thats fine if you want to downplay Mata if you dont rate him, but youre making statements without really backing it up.