Promoted Granada stunned champions Barcelona to move top of La Liga. Ramon Azeez headed in at the back post with less than two minutes played.
Barcelona manager Ernesto Valverde introduced Lionel Messi and Ansu Fati at half-time, but Alvaro Vadillo added the hosts’ second from the penalty spot after Arturo Vidal handled in the area.
The result condemns Barcelona to their worst league start for 25 years and leaves them in seventh, three points behind surprise leaders Granada.
Earlier, Atletico Madrid missed the chance to go top as they were held to a goalless draw against Celta Vigo.