Jones arrived Old Trafford over the summer in a £16.5million move, having impressed Ferguson in his last appearance at Old Trafford.
Despite being on the losing side of a thumping 7-1 Rovers defeat last November, Ferguson admits the youngster's maturity took him by surprise.
"When he was playing against us in the 7-1 game, after the fifth goal he was running out and giving everyone around him stick and he was only 18 then. I was very impressed," said the United boss.
"After that I tried to get him last January. We put an inquiry in but Blackburn wouldn't sell him at that time."
Jones will make his home debut at Old Trafford against Tottenham on Monday, and Ferguson has no concerns over his inexperience despite being without senior central defensive duo Rio Ferdinand and Nemanja Vidic.
"He was just one that we couldn't miss," said Ferguson of Jones. "He's definitely got all the parts to his game, there is no doubt about that.
"He has got the desire to play and he's a good trainer, with a great determination about him."