Tuesday's match at the Santiago Bernabeu will see the Portuguese face his former club as the two giants meet for the first time since an enthralling 6-5 aggregate Champions League quarter-final win for Madrid in 2003.
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"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," the defender told Uefa's official website.
"The fans appreciated him when he was here and since he's been gone they sing his name. He came here a young boy and left a world-class player. He showed a lot of respect when he left and still does."
He explained that defending against Ronaldo would be crucial to progressing, and continued: "You get as many people around the ball when Ronaldo’s got it as possible!
"Madrid are that good a side you have to make sure you're set up right and that your team are in good positions all over the pitch to defend.
"It'll be a game that everyone will be tuning into because there's so much attached to it."
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"In the away game – they really played us off the park if I'm honest," he stated.
"Raul was just difficult to get up against. In terms of making you think, he definitely was the most intelligent player I've played against."
The Red Devils failed to get past the group stage last year, and the year before saw a disappointing 3-1 defeat to Barcelona in the 2011 Champions League final at Wembley, the same venue for the climax of this year's competition.
"It'd be nice to go back there and put what happened last time right," Ferdinand said.
"We went there and we didn't give a great account of ourselves. Lionel Messi, in the two Champions League finals we played against him, was the main difference really."