The Argentina international faces a spell on the sidelines after sustaining a hamstring problem in Tuesday's win over Real Sociedad.
The 29-year-old was part of the Barcelona starting XI for the Liga clash but was forced to leave the pitch after 35 minutes after struggling with his right leg.
Mascherano underwent further examination on Wednesday morning and Barcelona has now announced that the former Liverpool man will be out of action for 10 to 15 days.
"Javier Mascherano underwent medical tests on Wednesday morning to determine the extent of the injury suffered in last night’s league match at home to Real Sociedad," a statement on the club's official website reads.
"It has been confirmed that he has sprained his right hamstring and will therefore be sidelined for 10 to 15 days."
Mascherano will consequently miss the Liga games against Almeria and Valladolid as well as the Champions League encounter versus Celtic.