Captain Carles Puyol has joined a long list of Barcelona absentees after feeling pain in his knee during training on Saturday, the champions said ahead of Sunday's La Liga game at home to Athletic Bilbao.
Centre back Puyol, who turned 36 this month, has barely played this season due to a string of injuries and coach Gerardo Martino is also without regulars including forward Neymar, goalkeeper Victor Valdes, centre back Gerard Pique and left back Jordi Alba for the match against fourth-placed Bilbao at the Nou Camp.
Midfielder Sergio Busquets is suspended but Marc Bartra, another centre back, has shrugged off a thigh problem and is in the squad, Barca said on their website (www.fcbarcelona.es).
Barca's hopes of a fifth La Liga title in six years suffered a major setback last weekend when they were beaten 1-0 at lowly Granada and slipped to third behind leaders Atletico Madrid and second-placed Real Madrid.
Atletico, who won 2-0 at home to Elche on Friday, are six points clear of Real, with Barca a point further back.
Atletico have four games left, including a trip to Barca on the final day of the season, while Real and Barca each have five.
As well as their reverse in La Liga, Barca were dumped out of the Champions League by Atletico last week and lost 2-1 to Real in Wednesday's King's Cup final, leaving them in serious danger of ending the season without major silverware.
"Our only option is to get the maximum points from the five games we have left," Martino told a news conference on Saturday.
"It is hard to keep our spirits up because we are not used to things like this," added the Argentine who is in his first season in charge.
"Regarding what we have ahead of us, we must believe we still have a chance.
"If the other two stumble that would give us some hope. Sadly, we lost the chance to depend on ourselves." Real's game at Real Valladolid originally scheduled for this weekend has been moved to May 7.