The 24-year-old was in the final stages of his comeback after initially sustaining a torn hamstring in the Catalans' 3-2 victory over Sevilla in September, with the club's medical staff asserting that a three-week lay-off was a probable absence for the Spain international.
However, the Blaugrana have now revealed that Alba is set for an additional six-week spell on the sidelines after suffering a similiar injury in the opposite leg.
The former Valencia starlet can expect to miss first Clasico of the season with rivals Real Madrid on October 26, as well as both clashes with AC Milan in the Champions League.
The news will come as a blow to coach Gerardo Martino, who has already been forced to contend with injuries to talisman Lionel Messi and utility man Javier Mascherano in recent weeks.
