The hosts showed a lot of determination to overturn a one-goal deficit and defeat the Spanish champions thanks to a late penalty from Xabi Prieto
Real Sociedad came from behind to upset Barcelona 2-1 in a fiery game at the San Sebastian, denying the Catalans the chance to go 11 points clear at the top of the table. The visitors, who fielded a number of youngsters and squad players in the first XI, took the lead in the first half through a brilliant chip by Thiago Alcantara.
Pep Guardiola's men pushed for more after the break, but were pegged back by an equaliser from substitute Diego Ifran, and ultimately lost the game after Xabi Prieto found the net from the penalty spot.
The hosts started the game well, defending high up the pitch and pressing Barcelona's midfield before Xavi & co. could muster anything dangerous. Real Sociedad even went close to scoring first when in the 16th minute Raul Tamudo flicked a cross wide of the right post.
However, Barcelona were settling fast into the game and started exerting their trademark passing style. The hosts looked water-tight at the back, but it seemed like a goal was just a matter of time.
The Blaugrana finally opened the scoring near the half-hour mark when Thiago exquisitely chipped Claudio Bravo after being picked out by Lionel Messi. Barcelona continued to press, but were finding it hard to bypass a tight defensive line by Real Sociedad.
Messi had a decent shot blocked in the 38th minute for what proved to be the final moment of interest in the first half.
Not much changed on the pitch after the restart as Barcelona seemed to be in full control of the game. Still, it was the Basque hosts who got the first chance in the second period when in the 47th minute Mikel Aranburu blasted a shot wide from outside the box.
The tempo of the game began to drop, but Barcelona were still the more adventurous team in attacking. Jeffren and Messi went close for the visitors in the following minutes, but both were denied by the excellent Bravo in goal for La Real.
Messi was at the heart of Barca's best attack in the second half when in the 65th minute he collected the ball deep in the visitors' half and raced all the way to the penalty area before squaring for Ibrahim Afellay, who under no pressure at all sent a weak shot right into the hands of Bravo.
Against the run of play, however, Sociedad got the equaliser through Ifran. The forward pounced on some hesitant defending by Gabriel Milito and Fontas to dink his shot over Pinto into the top right corner from near the penalty spot.
Milito had the ball in the net in the 76th minute with a diving header, but it was ruled out for offside as Barcelona were throwing everything forward in search of the winner. However, they were stunned six minutes later when Prieto converted a penalty conceded by substitute Javier Mascherano.
Following today's results, Barcelona sit top with an eight-point lead over Real Madrid, while Real Sociedad are 12th, two points ahead of Zaragoza. Guardiola's men host Espanyol next Sunday, while Sociedad visit Valencia a day earlier.