The Red Devils travel to Spain on Wednesday for the first leg of their last-16 tie with Madrid, a game that will mark Ronaldo's first meeting with United since leaving Old Trafford in 2009.
Ferdinand has admitted that Ronaldo will take some stopping but thinks that his side can use the Portuguese forward's strong relationship with United fans to their advantage.
He told reporters: "It's obviously going to be an emotional night for Ronaldo and a great night for him too. But hopefully it gets too emotional for him.
"We've had a few texts, but when you get into a situation like this when you're coming up against a friend, all the texts and the conversations go to one side and you don't really speak until you actually get the game over and done with.
"We're going to have to use all of our experience, courage and ability to make sure that we stop not only Ronaldo, but the other players they have, because Real are a great team."
Madrid have home advantage at the Bernabeu tomorrow night before United host the second leg next month.