The unfortunate Valdes, who has already confirmed he will leave Camp Nou to seek a new challenge at the end of the current campaign, was taken off on a stretcher during the first half against Celta.
Valdes landed awkwardly on his right leg when making a routine save from a free-kick and crumpled to the turf in agony.
The extent of the Spain international's injury has yet to be determined, but a lengthy layoff could rule Valdes out of the forthcoming FIFA World Cup.
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