The 31-year-old, who has been out with a broken hand since January, returned to training last week and was included in the Madrid squad for their last-16 second-leg encounter at Old Trafford.
"We will have to defend stoutly but we are here to attack, there is no doubt about that," Mourinho told reporters on Monday.
"Everyone is fit and ready to play with the exception of Iker Casillas. The emotion is high and it's a pity the match is not now and that we have to wait until tomorrow."
The first leg at the Santiago Bernabeu ended in a 1-1 draw.