City are one of the few clubs who could afford the £150million asking price if Ronaldo went through with his threat to quit the Spanish champions.
But Mancini said: "There is no chance. I don't know the situation with Ronaldo so it is very difficult to say something about him. But on Tuesday I would say it would be better for us if Cristiano stays at home!
"Players like Ronaldo and Messi are difficult to mark. You can do good work with your team, but these are players who score a goal in every game they play.
"It is hard for us because Ronaldo and Messi are the two best players in the world."