Ronaldo was whistled by his own fans during defeat to Barcelona and reportedly booed as he left the stadium, but Mourinho backed the Portugal forward to silence the doubters.
"During the game there is no time to listen to what happens outside. I do not think it's a big problem.
"He has been affected by losing a game, like everyone, but he has never lost the emotional balance. It is normal that today is sadder than a fortnight ago, but there is no drama in our situation."