Jordi Alba injured his hamstring in Barcelona's goalless draw against Slavia Prague on Wednesday. The left-back started the game but was taken off at halftime, replaced by Sergi Roberto.
"Alba has left hamstring discomfort," Barça confirmed in a statement. "He'll undergo further tests to determine the cause of the discomfort."
The defender will be checked at the training ground on Wednesday to determine how long he will be sidelined for, with Barça hosting Celta Vigo on Saturday before the international break.
Alba first felt the problem in the win over Real Valladolid and came off late on. He missed the weekend's loss to Levante, although he was on the bench.
Despite Alba's fitness issues, Ernesto Valverde has not turned to summer signing Junior Firpo. The former Real Betis left-back has not made the last two squads.
Instead, Valverde has opted to use Nelson Semedo at left-back and Sergi Roberto at right-back when missing Alba.