Barcelona captain Andres Iniesta will be out for six to eight weeks after injuring knee ligaments in the dramatic win over Valencia.
The midfielder was injured by an Enzo Perez tackle after 14 minutes of the 3-2 win and left on a stretcher.
He could miss the rest of the Champions League group games and is definitely out of the match at Manchester City on 1 November.
Barca won thanks to a late Lionel Messi penalty, his second goal of the game.
Luis Enrique’ side, who went top with the win, are also going to be without Iniesta’s fellow Spain internationals Gerard Pique and Jordi Alba through injury for the City game.