The former Atletico stopper returned to the Spanish capital and made a number of fine saves as United earned a 1-1 draw at the Santiago Bernabeu in the first leg of their last-16 clash.
"It's good for him to come back to Madrid and put in such a good performance," Giggs told BBC Sport.
"He is a top keeper and his shot stopping is second to none.
"He is maturing all the time and he has showed that. He has come to Madrid with a lot of pressure on him, being from Atletico, and he has produced the goods."
The return leg takes place on March 5 at Old Trafford.