Barcelona coach Pep Guardiola says beating Real Madrid on Saturday would be "a giant step" towards retaining the Spanish league title this year.
The Catalan club hold a commanding eight point lead over Real with seven games left and victory over their foes would virtually seal the league title, while a draw would still leave Madrid with a mountain to climb.
"If we obtain a good result we will take a giant step to reach the final and be champions again," he told a news conference on Friday ahead of the match.
"We have to have a really good match to be able to beat them. (Real coach) Jose Mourinho changes strategies frequently during matches so we have to pay close attention and adapt," he added.
"When you go to the Bernabeu you can't have a relaxed attitude, you have to be very ambitious otherwise they will run you over."
Saturday's match kicks off the first of four meetings between the two sides in just over two weeks.
The two sides will meet again on Wednesday in the Spanish Cup final which will be followed by their two-legged Champions League semi-final - with the first game at Real's Bernabeu stadium on April 27 and Barcelona hosting the second on May 3.