Real Sociedad inflicted a damaging 2-1 defeat on Barcelona at the Reale Arena on Sunday to tighten the La Liga title race.
Barcelona arrived in San Sebastian knowing victory would have preserved a narrow cushion at the summit, but they were left frustrated after an incident-heavy evening.
Sociedad set the tone inside the opening minute when the ball hit the net after 28 seconds, only for an offside flag to spare the visitors.
The early scare was followed by relentless chaos, with Barcelona missing chance after chance in the opening half-hour.
Fermin Lopez thought he had fired the visitors ahead, but VAR intervened to rule out the goal for a foul in the build-up.
Frenkie de Jong then had an effort disallowed for offside before Dani Olmo squandered a clear opening from close range.
Lamine Yamal appeared to add his name to the scoresheet shortly after, but that goal was also chalked off following another VAR review.
Sociedad absorbed the pressure and struck first just after the half-hour mark. Mikel Oyarzabal arrived unmarked at the far post to volley home a precise finish that lifted the home crowd.
Barcelona believed they had a route back into the match in first-half stoppage time when a penalty was awarded, but VAR again intervened to overturn the decision.
The second half followed a similar pattern, with Barcelona pushing and Sociedad holding firm.
Olmo hit the post twice in quick succession after the restart, while Alex Remiro was forced into sharp saves as the pressure mounted.
Barcelona manager Hansi Flick responded with a triple substitution just after the hour mark in an attempt to force a breakthrough.
One of those changes paid off when Marcus Rashford rose to head home an equaliser with 20 minutes remaining, briefly restoring control for the visitors. That optimism lasted less than a minute.
Goncalo Guedes punished slack defending at the back to restore Sociedad’s lead almost immediately.
Barcelona were rocked and needed a goalline clearance from Pau Cubarsi to prevent further damage after a defensive mix-up.
Jules Kounde later struck the crossbar with a powerful header as the visitors pressed desperately.
Sociedad were reduced to ten men late on when Carlos Soler was shown a red card for a challenge on Pedri.
Even with nine minutes of added time, Barcelona could not equalise. Rashford came closest again when his direct corner struck the post in stoppage time.
The final whistle confirmed a result that dents Barcelona’s momentum and cuts their advantage at the top.
