The Blues are five points clear of United at the top of the table and already have beaten their nearest rivals this season.
But on Ronaldo, Ancelotti says: "The numbers do not confirm this. United were two points behind Chelsea before our face-to- face; they have done well in the Champions League. Valencia, his (Ronaldo's) replacement, has great qualities and is starting to click with the well-oiled machine that is United. The only real disappointment (of the season) is Liverpool."