There was more disappointment in store for Barcelona as they threw away three points at Osasuna after a late strike from Chimy Avila secured a 2-2 draw for the hosts on Sunday.
Missing seven main players through injury, Barca manager Xavi Hernandez was forced to turn to his youngsters. Nico Gonzalez and Abdessamad Ezzalzouli, both 19, scored as the visitors twice took the lead.
Osasuna first levelled first through defender David Garcia. Avila then drove into the corner through a low shot from outside the box that deflected in off Samuel Umtiti's right foot for the draw.
Barca had earlier lost at home to Real Betis last weekend and were dumped into the Europa League by Bayern Munich on Wednesday. They have now ben held by Osasuna, who sit 11th and are winless in eight league games.
The Catalans are eighth in the table, still outside the European qualification places and 15 points behind leaders Real Madrid.
The pain for Xavi's team will be heightened by the manner of Osasuna's equaliser, coming so late after teenagers Gonzalez and Ezzalzouli had set them on course for victory.
Barcelona were ahead in the 12th minute when a shot from distance came back to Gavi, who had time to look up and spot Nico's dart in behind the Osasuna defence.
Two minutes later, Osasuna were level, as a flailing arm from Gavi into Kike Garcia earned the home side a free-kick out wide. Jon Moncayola swung it into the box, where Garcia rose high and headed into the corner.
Barcelona struggled to regain their rhythm but still went ahead early in the second. Osasuna wanted a penalty when Gavi's clearance struck the hand of Sergio Busquets but nothing was given and Barca broke fast.
The ball was spread right to Ousmane Dembele, whose chipped cross was flicked out of the reach of Frenkie de Jong but to the back post, where Ezzalzouli was free. He hooked the bouncing ball high into the net.
But it all went flat for Barca the 86th minute, failing to clear a cross and the ball spilling out to Avila on the edge of the area.