Javier Aguirre's side have struggled for form in recent weeks, but Casilla is confident that his side can upset the league champions at the Camp Nou.
"We all know how important the derby with Barcelona is. We will go to Camp Nou and try to go all out," he told reporters at a press conference.
"We'll have to play with intensity and try to stay focused for the entire 90 minutes. It's not going to be easy but it won't be impossible.
"I have total respect for the Barca players, but I am not afraid of them. If you're scared of playing against Barcelona then you might as well stay at home."
Barcelona have won 10 and drawn one of their 11 league fixtures this season.