Real are seven points clear after beating Real Zaragoza 3-1 and Barcelona drew 0-0 with Villarreal.
“We dropped two crucial points against Villarreal,” Valdes told Sport. “We simply have no more room for error. We have to win every point that is available to us.
“That’s the size of our task. If we want to fight for the title, we can’t slip up any more because there is a very strong rival above us.”