I think he already used him there in quite a few matches, though it depends on what you mean by 'central'. It's confusing because of all our switch ups, but when we were playing 5-3-2 I think he put Rooney in central midfield for the physical balance, so Mata could play as the most attacking midfielder in a midfield three.
I guess that's what he means with balance, he doesn't seem to like Carrick/Blind - Herrera - Mata as our midfield, if Herrera plays CM then he wants a physical player there with Fellaini, when Mata played in midfield he either played Rooney or Fellaini as CM.