The Galatasaray boss has acknowledged Wednesday's opponents have plenty of other attacking threats, but is glad his side will not have to face the in-form Real Madrid man
The 28-year-old, who already has eight goals in the competition this term from only four games, will not feature on Wednesday after limping out of los Blancos' 5-0 win over Almeria on Saturday with a thigh injury.
Madrid need only a point from their remaining two games in Group B to secure automatic progression to the last 16, but with second-placed Galatasaray and bottom side Juventus separated by only a point, Mancini is well aware that any slight advantage could be key.
The Italian told reporters: "Ronaldo, of course, is a very important player. His absence is an advantage for us, but we know that Real Madrid have many key players.
"We have to look at ourselves. It does not matter what your opponent does. There is a great chance to qualify from the group in front of us. We are confronted with a significant atmosphere in the Bernabeu, but we must focus."
Gala, under former coach Fatih Terim, were beaten 6-1 at home in the first meeting between the two sides back in September.
However, Mancini insists he will read little into that result, while revealing Wesley Sneijder could start at the Bernabeu after making a quick recovery from a thigh problem.
"You cannot compare the first game to this match," he continued. "They scored six goals but both teams are now very different - we have to make better use of the opportunities we make.
"Sneijder is in good condition. He has worked with the team for the past four or five days. He is a major player and I will make a decision as late as possible over whether he will play."