Kaka hit two penalties in the triumph.
Karanka said: "He played a great game, as did Pepe. He looked good, especially after all the things that happened with him in regards to his injury. It is important that Kaka is fit because there are important games coming up."
Karanka also took time to acknowledge the contribution of Argentine winger Angel Di Maria, who has been in excellent form of late:
"Di Maria is a player who never leaves anything on the pitch. He always gives 120%. He had a great game and did everything for the team, which was important for us."