Javier Mascherano will miss Argentina's summer friendlies against Brazil and Singapore after he injured his knee in the Copa del Rey final against Alaves.
Mascherano was taken off in the early stages of the 3-1 win at the Vicente Calderon on a stretcher following a clash of heads with Marcos Llorente.
The club later said he'd suffered concussion but after further analysis on Sunday they were also able to confirm that damage to his knee will keep him out of action for over a month.
"Tests carried out on the Argentine international have revealed that he has a posterior capsule strain in his right knee," a statement read. "The player will be out for six weeks."
Barca's season ended with the win over Alaves but Mascherano was due to report for international duty for Jorge Sampaoli's first games in charge of La Albiceleste.
Argentina travel to Australia to face Brazil in a friendly match on June 9 and then play in Singapore on June 13.
Mascherano should recover in time for preseason with Barca, though, which will begin with a new manager after Luis Enrique took charge of his last game this weekend.
President Josep Maria Bartomeu has already confirmed that Luis Enrique's replacement will be announced on Monday, with Ernesto Valverde, who left Athletic Bilbao last week, the clear favourite for the role.