The 27-year-old, who is the Blancos' top scorer this season with 19 strikes, failed to add to his tally against the Basque side, with Karim Benzema, Sergio Ramos, Mesut Ozil and Sami Khedira sharing the goals amongst themselves.
However, the assistant coach has no issue with the forward's failure to find the net or supply an assist and instead pointed to his overall efforts in helping the team make easy work of their victory to stay eight points behind Barcelona.
|10/3||Cristiano Ronaldo is 10/3 with William Hill to win the 2012 Fifa Ballon d'Or
"We have already spoken too much about Cristiano's importance to the team," Karanka said after the match. "He may not have scored today but he was still generous as ever."
The former Spain defender then gave his thoughts on the progress made by summer signing Luka Modric and on-loan midfielder Michael Essien.
"Modric is very talented and is growing each day," Karanka. "Essien has played in almost every position for us, now we need to find his best one."
Real Madrid striker Jose Callejon also stuck up for Ronaldo during the emphatic victory, reiterating Karanka's statement that the attacker was generous and insisting the ex-Manchester United man was satisfied with his showing.
"We support him as we always do," Callejon said. "He is very happy with the win and was always ambitious. Though he did not score, he gave assists, participated and was generous."