"I think Cristiano has come to accept that at this stage of his career, United is the place for him.
"But once we had talked he accepted it was a move for the future.
"I pointed out to him how much better it would be to leave like Eric Cantona, with the fans loving and appreciating him.
"The crowd still chant Cantona's name and I told Cristiano 'Leave a hero like Eric' and one day he will. But not yet."
Adam Johnson equalised Ronaldo's header with a powerful second half volley but Pogatetz's departure affected Middlesbrough more than United and the hosts had got on top before Giggs took advantage of Gary O'Neil's slip 11 minutes from time and Nani sealed a place in the fourth round in stoppage time.