Barcelona on Friday confirmed that midfielder Xavi Hernandez will be out for "10 to 15 days", ruling him out of Saturday's Clasico and rendering him doubtful for the Champions League last 16, second leg, against AC Milan.
The Spanish top-flight leaders announced on their website that Xavi is suffering from a slight tear in his right hamstring.
While his absence from Saturday's trip to play Real Madrid at the Santiago Bernabeu was expected -- and not a major blow with Barca currently 12 points clear at the top of La Liga -- he would be sorely missed against Milan.
The Catalans are 2-0 down from the first leg of their tie against the Italian side and face a huge task to keep their Champions League hopes alive.
The return leg at the Camp Nou will be played on March 12.
In his absence, Thiago Alcantara is likely to stand in against Madrid, and possibly for next Saturday's home meeting with struggling Deportivo.