The French ace told Sport magazine: "This is the most important game of our season - especially since Chelsea have never been in a Champions League final.
"We beat them 2-1 at Stamford Bridge recently, so we are quite confident.
"But they have Ronaldo, of course, who is brilliant.
"United play great football and as a result he always manages to find the gaps.
"He shines when he has the whole team playing around him but he also shines when he is alone.
"He can often make the difference on his own, so it is hard.
"But we have good defenders and we hope he has a bad day."