The Brazilian left-back has called on his former club to prove their worth against Barca, while Samuel Eto'o thinks that Madrid have the advantage in Wednesday's first leg
The Santiago Bernabeu outfit host their Catalan rivals on Wednesday in the first leg of their quarter-final match-up.
Roberto Carlos, who played at the Santiago Bernabeu between 1996 and 2007, says that the time is right for los Blancos to turn the tables in Spanish football.
"Madrid have great players and they must be calm on the field," he told Marca. "The time has come for Madrid to change history.
"I see the same Barca as always. Their players know each other very well and they can create problems in two minutes. Beating them [on Wednesday] will be hard."
Meanwhile, Samuel Eto'o, who had spells at both Madrid and Barca, expects Jose Mourinho's men to attack in the first leg in front of their own crowd.
"Playing at home has to be crucial, just like when I was playing in Spain," Eto'o said.
"At the Bernabeu, Madrid must be fearless and more offensive. They are obliged to win and then they will have to wait and see what happens at Camp Nou."
Wednesday's Clasico kicks off at 22.00CET.