Sanchez sustained a serious ankle injury on international duty in a friendly for Chile.
Sanchez hobbled off in the 88th minute in the 0-0 draw against Colombia.
Sanchez suffers serious ankle injury: Inter Milan
"Alexis Sanchez underwent medical tests earlier this morning at the Humanitas Institute in Rozzano. Results revealed a joint dislocation in his left ankle which has caused damage to the peroneus longus tendon," a statement read.
"The player will meet for further consultations with Professor Ramon Cugat in Barcelona on Wednesday, where they will seek to reach a decision on whether surgical intervention is necessary."
Sanchez likely to be out for a long time
Meanwhile, Chile coach Reinaldo Rueda said the forward could be out for up to three months.
"We have to see what diagnosis they make in the club, because it is decisive for us," the Chilean coach said.
"If there is surgery we could lose him two to three months, if not, it could be a matter of weeks. That depends on the club."