The Northern Ireland youngster impressed in the 0-0 draw with Villarreal on Wednesday.
Fergie said: “It was a good night for him and it’s an indication of his quality.
“We had offers for him from three or four clubs in the summer but we stuck to our guns because we believe in him.
“Jonny will be the future centre-half for Manchester United, there’s no doubt about that.
“That’s a vindication of our belief in the boy and also proves that he can believe what we’re saying to him — he’ll play a lot of football here.”
He added: “He’ll get plenty of games and his performance on Wednesday gave me an idea of how to approach the match against Chelsea on Sunday.
“He’s only 20 years old but he’s already got around 10 international caps.
“Jonny will be a fixture for Northern Ireland now and I imagine he’ll be their captain in time — he’s an outstanding candidate for that.
“He’s a boy with a great talent and we’re very pleased with his progress.”
