Betis' flying start to the season was punctured before the international break with defeats to Getafe and Levante ending a four-match winning streak which had seen them top the table on their return to the top flight.
"We can say we are a team with a style and a strong footballing philosophy," he told the Diario de Sevilla newspaper.
"Not all teams can boast that and we will not change anything just because we will face one of the best teams in the world."
Beating Jose Mourinho's title challengers would represent a significant coup for Betis but Casto insists playing Madrid is no different to any other Primera Division clash.
"It is just as important to beat Real Madrid as it is Levante," he said. "It is one more game, three points.
"I don't think of beating one team in particular and we believe in ourselves to give them a good game."