Nobody expected that result, but it should be noted that this is the second game without Yamal in the lineup and the second defeat of Barcelona, apparently the dependence on Yamal is very serious, if without him Barcelona can not score and moreover, Barcelona has not been able to score a single shot on goal Real Sociedad, which is strange for the leader of La Liga.
There was also a controversial decision of VAR when they canceled the clean goal of Lewandowski, because the picture shows that the foot of the Real Sociedad defender was offside, so the referee's mistake seems to have helped Real Sociedad to win.
Many of us are surprised by this result which we know on paper Barcelona is far superior to its opponent especially in this season they are very consistent many strong teams have become victims but when playing against Real Sociedad Barcelona seemed helpless I do not understand what the reason behind the defeat but maybe as you said Yamal's absence the attack built by Barcelona was not so effective as proven from 11 shots none of them hit the target, the only best chance was a goal that was disallowed by the referee. And not only you I also question the controversial decision.
The referee decision was just awful and although there is no excuse for such a poor performance from the Barcelona players, the referee still took away one clean goal from Lewandowski.
I read the statistics and the last match when Barcelona failed to hit the goalposts was in 2014 and then Barcelona was still coached by Luis Enrique.
I hope that Flick will be able to understand what happened to the team and learn from this defeat, besides now there will be almost 2 weeks break and time to change something in the game of the team will be enough.
I would like to see the former Barcelona with a beautiful attacking game and scoring goals.