Nelson Valdez struck twice for Hercules to shock Barcelona 2-0 last night.
Valdez gave the Alicante-based outfit the lead when he poked home from a free-kick against the run of play after 26 minutes.
And the Paraguay forward, making his debut for the visitors, silenced the Nou Camp with a superb second on the hour to give Hercules a two-goal lead.
Barca attacked ceaselessly in the final half hour, but came up against an inspired figure in the Hercules goal.
"I congratulate Hercules. They came here and played well. They made it difficult for us and they got their reward," Barca coach Pep Guardiola said.
But the Barca coach admits his side produced an off-colour performance in their first home match of the Primera Division campaign.
"We lacked our usual fluidity. There are so many details we can improve on. We'll have a look at it and try to overcome it. We have overcome so many things since I've been here and we will again," he said.