MADRID • European champions Barcelona were stunned by an Aritz Aduriz hat-trick and a brilliant opener from Mikel San Jose as Athletic Bilbao took a 4-0 lead into the second leg of the Spanish Super Cup on Friday.

Barca had picked up their fourth trophy of the year on Tuesday, beating Sevilla 5-4 in extra time for the Uefa Super Cup, but those exertions took their toll as they were overpowered from the opening whistle.

San Jose fired in a volley from just inside the Barca half to break the deadlock, before Aduriz struck three times in 15 second-half minutes to give Ernesto Valverde's side a huge advantage heading into tomorrow's second leg.

"To score four against Barcelona is almost impossible. We are very satisfied with our work but the second leg is still to come and it is going to be very tough," Aduriz said.

"We cannot think that Barca can't score four goals in their home stadium. They are the best and capable of doing anything."

With defensive lynchpin Gerard Pique among four first-team regulars rested, Barca were shambolic at the back, and this time could not be rescued by an off-colour Luis Suarez and Lionel Messi.

It is the first time in 14 years that the Catalans have conceded four times in two consecutive games.

"It is going to be difficult, but we have won many matches by many goals and we will try until the last minute," said a defiant Javier Mascherano. "They had four or five chances and scored four. But don't count us out yet."

AGENCE FRANCE-PRESSE