"The Champions League? It depends, it is a competition where the difference between winning and losing is very small," Mourinho told Bein Sport.
"I do not believe that anybody thought that Chelsea last season would have won it. But, they did and I was happy because I have a blue heart.
"It is necessary that we make it to the quarter-finals or semi-finals. And then from there, anything can happen."
Madrid have reached the semi-finals of the Champions League for the past two seasons.