The goalkeeper was left aghast at the way his side capitulated against Real Sociedad and admits the international break will provide some welcome relief.
The Champions League holders raced into a two-goal lead inside 11 minutes at Anoeta before a complete capitulation saw them suffer a 4-2 defeat.
Madrid's set piece defending was once again in the spotlight as La Real exploited the uncertain Sergio Ramos and Pepe, but Casillas has called on the entire team to improve their efforts following the collapse.
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"First, I have to congratulate Real Sociedad, who played a spectacular game," he told Canal Plus. "Our team was horrible. From two goals up, you cannot finish the game in this way, it is not the way nor the attitude to move forward with.
"We have to pay more attention because everyone is at fault and not just those at the back because all the team are needed to defend."
The Spain veteran admitted the international break will come as something of a relief as Madrid aims to forget a result which has seen it already slip behind Barcelona and Atletico Madrid after two rounds of La Liga.
Casillas said: "We will be outside all the discussions and what the journalists say. We do have to pay attention to the voices from inside, though, because what happened in this match is not normal."