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

Barca had picked up their fourth trophy of the year in Tbilisi on Tuesday with a 5-4 win over Sevilla in extra time in the UEFA Super Cup.

But those exertions clearly took their toll as an under-strength side was dominated from the off by the Basques.

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 Monday's second-leg.