Barcelona have confirmed Ibrahim Afellay will require an operation after the winger tore a ligament in his left knee during training.
It is another injury blow for the Dutchman, who had recently returned to fitness after picking up a hamstring injury in the pre-season.
The 25-year-old has played just substitute roles this season, appearing in games against AC Milan and Osasuna.
"Bad news for Josep Guardiola and FC Barcelona," the club said in a statement on Thursday night.
"Ibrahim Afellay has torn a cruciate ligament in his left knee while training this evening.
"He will require surgery and further details will be revealed tomorrow (Friday) regarding how and when."