"He has without question all the qualities to be a Manchester United player. His progress over the last few months has been outstanding," the United boss said at a press conference in Rome.
"We've only be able to judge him in training and a couple of appearances in the first team.
"But he's quick, aggressive, has a fantastic attitude, he's a very good defender and he's improving his technique all the time."
Ferguson said that a good attitude was the most vital quality a player needs to be able to break into the first team set-up.
"For most of the young players brought into the first team it is a prerequisite to have a good temperament," he said.
"That's something we judge through their development as young players so there was never any question as far as temperament was concerned (with Simpson)."