Tito Vilanova's side are currently eight points clear of Atletico Madrid in second, as they look set to reclaim the Primera Division title from Real Madrid.
The defeat for the Catalan club was their first league loss of the season and early in the first half it looked certain that their unbeaten run would continue as they took a 2-0 lead. Sociedad grabbed a goal before the interval before equalising in the second half, setting up an injury-time winner to secure a remarkable comeback.
After the defeat, Barca assistant manager Jordi Roura said he was confident will bounce back.
"I have no doubt that we'll give it our all, but this is football. I'm sure that the team will react well," he said.
Osasuna, third from bottom, welcome new loan signing Francisco Silva as they continue to battle for survival. The Chilean midfielder is on loan for the remainder of the season after joining from Universidad Catolica.
"It's my first experience in European football and I have to adapt as quickly as possible, because time is short and I hope to make the most of it," he told the club's website.
Atletico Madrid travel to Athletic Bilbao as they look to close the gap on the leaders. In the build-up to the game Atletico striker Adrian claimed he was paying little thought to the speculation linking him with a move to Arsenal. A clause in his contract means the 25-year-old is free to leave if a bid is received for 18 million euros (£15.1million).
"I try to isolate myself from the rumours," he said. "We are used to them and do not take them seriously. I am very happy at Atletico.
"I am happy here and it is my intention to continue here.
"The good thing at the moment is that the team is doing very well. I would like to stay for a while yet."
Bilbao's prized asset Fernando Llorente has agreed a deal to move to Juventus at the end of the season after his contract expires with the Basque club.
Real Madrid's season of struggle continues as goalkeeper Iker Casillas has been ruled out of the game against Getafe. The Madrid captain fractured a bone in his hand during Wednesday's Copa del Rey clash against Valencia and will now have an extended run on the sidelines.
"After carrying out initial x-rays at the La Moraleja Sanitas Hospital it has been confirmed that the footballer Iker Casillas has suffered a fracture at the base of the first metacarpal on his left hand," a statement from the club read. "It will be assessed again by a specialist later today to decide what treatment will be followed."
There has been no timeline given for the injury, but one of this nature tends to take up to three months to heal.
The weekend' s action starts off with Celta Vigo, who are a point off the relegation zone after securing a 1-1 draw at Champions League-chasing Malaga, hosting Real Sociedad.
The rest of Saturday's fixtures see Levante host Valladolid, Espanyol travel to Real Zaragoza and bottom club Deportivo La Coruna hosting Valencia, who have won three out of their last four league games as they look to push for a Champions League place.
Sunday's 4pm clash will see Rayo Vallecano and Real Betis battle it out as both teams look to cement claims for a European place come the end of the season, with the home side in sixth four points off their visitors who currently occupy the final Champions League spot.
Relegation-threatened Mallorca will host Malaga, while the Monday night clash will see 16th-placed Granada travel to 12th-placed Sevilla.