The Barcelona midfielder stated earlier on Friday in a video leaked to the press that "Madrid's players did not know how to lose" after the 4-3 aggregate defeat to the Catalan side in the Copa del Rey quarter-finals.
"Madrid have always been used to winning, not losing," said Karanka, who spoke to reporters instead of Jose Mourinho in Friday's press conference.
"Everyone knows what they say. My job is not to comment on what others say."
Karanka then heaped praise on Madrid's display against Barca in mid-week, but warned his side against complacency ahead of Saturday's match against Zaragoza.
"We gave a spectacular account of ourselves," he added. "We have to focus on that and think about the next match, which is tomorrow's match against Zaragoza, which will be hard.
"Last year they surprised us at the Santiago Bernabeu."
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