Van Nistelrooy and Ferguson fell out in 2006 and the Dutchman was forced to leave United.
He said: “I had been thinking about it for a while and talking it through with my wife.
“She suggested I sent Ferguson a text message to see if he was willing to talk so I sent him a message asking if I could call and he replied to say: ‘OK, call me at this date and time.
“I rang him and he answered and said: ‘OK, go ahead’.
“I said I wanted to apologise for what had happened and he said ‘OK, I appreciate that, when we meet again it will be OK’.
“Two or three times every year I would think to myself what a shame it was that it ended like it did with Ferguson. I wanted to do something about it.
“I was really pleased with the phone call.
“I said to him: ‘Those five years at Man United were fantastic, and working with you, and it’s unfortunate what happened’.
“If I encounter Ferguson again – and I really hope that will happen – I will embrace him and then it will all be finished.”