Barcelona thrashed 4-0 by Bilbao
Athletic Bilbao destroyed Barcelona in the first leg of the Spanish Super Cup as Aritz Aduriz netted a hat-trick in an extraordinary game.
Mikel San Jose opened the scoring after 13 minutes with a magnificent strike from the centre circle after an error from Barcelona keeper Marc-Andre Ter Stegen.
Barcelona's inexperienced line-up then shipped three goals in a torrid second 45 minutes, leaving them with a huge task of overturning the deficit in the second leg on Monday at the Nou Camp.
It is the second time in two matches that Barcelona have conceded four goals, after their 5-4 victory over Sevilla in the Uefa Super Cup.
And the nature of this humiliating defeat will concern coach Luis Enrique as his side prepare to mount a defence of last season's Treble - with their opening La Liga fixture coming against Athletic Bilbao at the San Mames.
San Jose scores a screamer
Barcelona's evening began to unravel when midfielder San Jose capitalised on an error from goalkeeper Ter Stegen to give Athletic Bilbao the lead in spectacular fashion.
Ter Stegen raced out of his area to head the ball clear, but the ball landed in the centre circle at the feet of San Jose, who hit an unstoppable dipping half-volley over the stranded Barcelona keeper.
The Spain international spent three years at Liverpool but never made a senior appearance for the Reds.
Enrique's inexperienced line-up
Luis Enrique had opted for an inexperienced line-up, handing starts to fringe players Sergi Roberto and Marc Bartra, although Lionel Messi and Luis Suarez played the whole game.
With the likes of Andres Iniesta and Gerard Pique on the bench, Bartra was partnered at centre-back by former Arsenal captain Thomas Vermaelen, making only his second appearance for Barcelona after an injury-hit campaign last season.
But the decision backfired on Enrique as his experimental team struggled to cope with the relentless pressing of Ernesto Valverde's well-drilled Athletic side.
Messi was far from his best in the unfamiliar line-up, but he did produce a superb free-kick just before half-time that was brilliantly tipped over by Gorka Iraizoz.
Aduriz nets hat-trick
After half-time it was one-way traffic as Athletic seized control of the tie.
They doubled their lead when Aduriz got above Javier Mascherano to power in a header after superb work by Sabin Merino on the left flank.
The hosts were rampant and they added a third when Barcelona failed to deal with a cross and the ball fell to Aduriz eight yards out, who swivelled and smashed in a superb volley.
And the visitors' misery was complete when Dani Alves was penalised for an off-the-ball push at a corner and Aduriz confidently slotted in the resulting penalty for his hat-trick.