The 22-year-old has featured in seven Premier League games and two Champions League fixtures for the Red Devils, and has established him as a first-choice right-back.
"He is maturing and learning all the time," Ferguson told Sky Sports News.
"Rafael has all the ingredients of a great player. He is blessed with great enthusiasm, skill and speed.
"He was quite impulsive and tended to over-commit himself. We have gone over it a few times but, bit by bit, it is all coming together and he was easily our best player Saturday."
Rafael joined United from Fluminense in 2008.