Hector Bellerin has suffered a calf strain in training as Barcelona's injury problems continue to mount.
Barca had largely been able to select from a full squad during the early weeks of the season, but the past week has given head coach Xavi plenty of fitness concerns to contend with.
Bellerin is the latest to sustain an issue, with the right-back suffering difficulties with his calf during a training session on Tuesday.
A club statement said Bellerin is to "undergo a series of tests to determine the full extent of the trouble", though it would be reasonable to assume he is a doubt for Saturday's trip to Mallorca.
He is the third Barca defender to suffer an injury in the past week, with Jules Kounde out until mid-October with an Achilles problem and Ronald Araujo not expected to play again until after the World Cup following thigh surgery.
Also sidelined are Frenkie de Jong and Memphis Depay, who were injured on international duty with the Netherlands.
Barca's injury problems are mounting at a particularly inopportune moment given how hectic October promises to be.
Next month, Barca will face Inter twice and Bayern Munich again in the Champions League, while they have El Clasico and potentially tricky clashes with Villarreal, Athletic Bilbao and Valencia all in LaLiga.