Neymar opened the scoring in the fourth minute before two more goals from Lionel Messi and Sergio Busquets inside 25 minutes left Real Sociedad reeling at the Camp Nou.
The Brazil forward made the most of hesitation between two Sociedad defenders and goalkeeper Claudio Bravo to rush forward and poke the ball home for his first goal since joining the champions in the close season for 57 million euros ($76 m).
Messi lunged headlong four minutes later to score past Bravo from Neymar’s cross for his seventh league goal this season.
A minute later Bravo was forced to sprint forward and punch away a head-high ball as Neymar arrived alone into the penalty area. Sociedad captain Xabier Prieto fell to the ground clutching his right thigh and had to be substituted in midfield by Imanol Agirretxe in the 21st.
Busquets scored Barcelona’s third two minutes later after the ball had bounced off the crossbar from Messi’s close-range shot. Sociedad pulled one back when Agruirretxe beat Gerard Pique and passed the ball across the goalmouth for Alberto de la Bella to tap into goal past a stranded Victor Valdes in the 64th.