The 32-year-old German international was stretchered off after falling awkwardly during his team's 5-1 victory over Villarreal on Sunday.

"(Ter Stegen) has a complete rupture in the patella tendon in his right knee," said Barcelona in a statement.

"On Monday afternoon he will undergo a surgical process and once complete a new update will be released."

Ter Stegen, who was criticised after making a mistake in Barcelona's 2-1 Champions League defeat at Monaco on Thursday, suffered the injury before half-time at Villarreal's Estadio de la Ceramica.

"I think it will be a huge injury, when he lay down on the field... you can see it directly," Barcelona coach Hansi Flick said after the game.

Inaki Pena replaced Ter Stegen and is set to fill in for the German, although Barcelona may look to sign a replacement.

Flick said it was too soon to comment on the issue.

"I don't know if I like this question directly after the match... I just want to see how Marc is, he's our captain and is a very important player for us," said Flick.

"Please understand that I don't want to talk about that."

Ter Stegen started two Nations League matches for Germany in September after Bayern Munich veteran Manuel Neuer's retirement from international duty in August.

(For more sports news and updates, follow Ahram Online Sports on Twitter at @AO_Sports and on Facebook at AhramOnlineSports.)