The Chile international limped out of his country's 3-1 defeat to Serbia after 20 minutes following a challenge from Luka Milivojevic with tests immediately pencilled in to determine the extent of the damage.
And Barca will not be pleased to hear the former Udinese man has been diagnosed with a sprained ligament in his right foot.
He is set to miss up to eight games, the domestic fixtures against Real Zaragoza, Levante, Alaves, Athletic Bilbao, Real Betis and Atletico Madrid and the Champions League clashes with Spartak Moscow and Benfica.
His absence will be a blow for Barca boss Tito Vilanova whose squad is short of strikers.
David Villa is the only senior 'number nine' at his disposal although he does have a wealth of attacking midfielders who can be pushed forward if required.