Athletic Bilbao midfielder Ander Herrera faces a period on the sidelines after suffering a hamstring injury in training.
The 24-year-old, who has had a dip in form since being linked with a move to Manchester United in the summer, suffered the strain during a training session with Bilbao on Friday.
The severity of the injury is currently unclear, but it is understood that the Spaniard could be out of action for the next two weeks.
Herrera joined Bilbao from Real Zaragoza in 2011.