Barcelona assistant coach Jordi Roura has questioned referee Alberto Undiano Mallenco.

Roura pointed out that Undiano, appointed for tonight's Copa del Rey second-leg clash with Real Madrid, had taken charge of Barca's only league defeat this season - when Gerard Pique was sent off in a 3-2 defeat to Real Sociedad in January - and also recalled his stewardship of the 2011 Copa del Rey final, won 1-0 by Real Madrid in extra-time.

"It is evident that with Undiano our numbers are always worse than with others," Roura said. "And we keep in mind his permissiveness in that Copa final.

"But we must wish him luck. What we are concerned with is Madrid."

Roura expects Undiano to be kept busy due to the special intensity of matches between the great rivals, but hopes the officials do not steal the limelight.

"We hope that their decisions do not decide the match and that they go unnoticed," he said. "Every Clasico is intense, hard. But we hope it won't run out of hand and that it stays within the sporting limits."