The Portugal captain will arrive at the home of his former club Manchester United, who he left for Madrid in 2009 for a record £80m, on March 5, but he will try to give the Spanish giants an advantage in the round-of-16 tie in the first leg tonight at the Bernabeu.
"Ronaldo's a great player and he can make the difference," The Express quotes Wenger as saying. "But he is up against his former club and that will put him in the eye of a hurricane. We'll have to see just how he faces up to the return at Old Trafford.
"You could say that Real Madrid have an advantage in that they are not competing for the La Liga title and so they can concentrate on the Champions League. But on the other hand it is logical to assume that United have been resting players, and keeping their best tricks up their sleeves for this tie."