Ferguson said: "What they've shown at the moment is that no one turns them over. They don't get stupid scores.
Hughes, Barclays Manager of the Month for October, played 345 times for United in two spells and has subsequently established himself as perhaps the most promising manager among the host of United old boys who have progressed to coaching.
"Maybe three years ago there was a bad season discipline-wise, but it can't be like that all the time.
"Their discipline this season and last season has been very good. That's a tell-tale sign, really. There's nothing wrong with being aggressive if it's the right kind of aggression.
"He was always a determined player. He was Rottweiler on the pitch, a real warrior. But off it you couldn't find a quieter guy. It was like a split-personality thing."