Barcelona centre-back Gerard Pique will be out for "two to three weeks" after hurting his left foot in his side's 3-2 win at home to Spartak Moscow in the Champions League on Wednesday, the club announced.
The 25-year-old Spain international was injured in a challenge with Spartak midfielder Romulo in the 11th minute at Camp Nou and had to leave the field, with Alex Song taking his place.
Pique's injury leaves Barca very light in central defence, with Carles Puyol already sidelined for between four and six weeks due to a knee injury sustained in Saturday's 4-1 La Liga win at Getafe.
Puyol has already been ruled out of the Clasico against Real Madrid on October 7 and Pique's participation in that match is now also in doubt.
With Puyol and Pique both out of action, Barca have only two senior centre-backs at their disposal in the form of Javier Mascherano, himself a converted holding midfielder, and 21-year-old youth team graduate Marc Barta.