"You'll never break Cristiano Ronaldo - he's the strongest man in football," he told The People.
"I know Cristiano well and I know the type of person he is so I have no doubts about how he will handle himself in the next few weeks.
"People must understand that Cristiano becomes stronger with all his difficulties and the stories about him. I have never known anyone so mentally strong.
"What happened to him at the World Cup in 2006 in the quarter-final against England would have crushed many other players - but not Cristiano.
"And what has been happening around him here with the uncertainty about his future has not affected him - I know that because I have been with him.
"He is so strong mentally and he is in control of his own destiny - and because of that Manchester United can do nothing to hurt him."