Valencia defender Bruno is expected to be sidelined for four weeks with an ankle injury.
The right-back picked up the problem in Saturday's 1-1 draw with Sporting Gijon and had to be replaced midway through the second half.
Scans have confirmed the extent of the damage and Bruno will not be able to return to action for about a month.
Bruno will therefore miss a number of important Primera Liga matches as well as both legs of the Europa League tie against Club Brugge.
Manager Unai Emery said: "This is the worst time for injuries because the team is playing for its life in some competitions and every man is necessary."