Real Sociedad brought an end to Barcelona's unbeaten La Liga record this term after pulling off a 3-2 victory over the visitors on Saturday night.
The Catalans were two goals clear early in the clash and seemed to be cruising after Lionel Messi and Pedro's strikes. However, Chori netted a double and Imanol Agirretxe provided the winner in stoppage time.
Barca took the lead as early as the seventh minute when Messi pounced on a poor clearance from Claudio Bravo and slotted from the edge of the area.
Xabi Prieto almost responded immediately with a shot into the side netting of Barca's goal, but Pedro doubled the lead at the other end of the pitch. Dani Alves curled in a superb cross that picked out Pedro, who finished from close range.
Messi came within inches of making it 3-0, but his dink over the goalkeeper hit the post instead.
In the 41st minute the hosts were back in the game as Chori opened their account. He controlled a Carlos Vela cross inside the box and fired home.
Eleven minutes into the second half the visitors were reduced to 10 men when Pique was shown his second yellow card for a trip on Vela.
The hosts took advantage of their superior numbers as Chori's deflected shot found the back of the Barca net in the 63rd minute.
The tie looked set for a draw with time running out, but in the dying moments Carlos Martinez found Agirretxe with a cross and the striker did the rest with cool finish.