The Spanish glovesman tried to take some of the pressure off his side and stressed that the club will not leapfrog Los Blancos in the table even if they win the match
The Catalan giants defeated Levante 2-1 on Saturday to remain four points shy of leaders Real Madrid, who saw off Sporting Gijon 3-1.
With only five matches remaining in La Liga, the Clasico at Camp Nou on April 21 may decide the outcome of the tournament, but Valdes has reiterated that Barcelona will remain second after the match even in the event of a victory.
"The Clasico will be very important, but not decisive," Valdes told reporters after the Levante victory. "Even if we win, we will still not depend on ourselves to win the league.
"The week we have ahead is one of those which give this job a meaning."
Prior to the crunch game against Madrid, Barcelona will visit Chelsea in the first leg of their Champions League semi-final tie on Wednesday.