The Red Devils spent big over the summer in an effort to force their way back into the elite group of challengers capable of competing for the top-flight crown.
A record-breaking deal brought Paul Pogba back to Old Trafford from Juventus, while the presence of Jose Mourinho in the dugout helped to lure Zlatan Ibrahimovic to England at the end of his PSG contract.
Mills feels both of those acquisitions are of the required standard, but would only put goalkeeper David de Gea alongside them in that bracket.
