Ronaldo was subdued as Real ran riot over Bilbao.
Karanka insisted: "I don't think that Cristiano ever has to justify anything to us. We know him very well and we have spoken of what is for this team too many times. Those of us in there, living with the team, know how important he is.
"He did not score in this match but made some assists, he was very generous. When he scores goals it often to win matches, and today he was not there to score but to create them, to move and to open spaces."