Gerard Pique is to be sidelined for up to three weeks after sustaining an injury in Barcelona's 3-2 win over Spartak Moscow.
Pique, 25, injured his left foot in the early stages of the Champions League group stage match at the Camp Nou.
After attempting to play on, the Spain international was forced off in the 12th minute, with summer signing Alex Song replacing the defender to partner Javier Mascherano at the back.
Pique is now a doubt for Barca's Clasico meeting with Real Madrid on October 7, which will concern manager Tito Vilanova, who is already without the injured Carles Puyol.
With Puyol and Pique both sidelined, Barca have only two senior centre-backs at their disposal in Javier Mascherano and 21-year-old Marc Bartra.