Karanka said: "We will continue fighting and winning matches out of respect for everyone.
"This is the track we need to be on. Every match is different. Playing a Copa tie isn't the same as a league match or a final.
"Every referee is different and [last night's] was a pleasure to play with. He lets teams play, which makes for fun, uninterrupted matches to watch."
Of Ronaldo's contribution, Jose Mourinho's number two said: "Cristiano capitalised on his talent. Nothing concerning the Pichichi [the trophy awarded to the top goalscorer in La Liga] has been pre-arranged.
"The match just unfolded like it did. We scored six goals against Valencia and he didn't score any of them."