Athletic Bilbao striker Inaki Williams suffered a hamstring injury in their UEFA Europa League clash with Zilina on Thursday.
There was injury added to insult for Athletic Bilbao, with promising striker Inaki Williams injuring his right hamstring in their UEFA Europa League outing.
Bilbao were 3-2 losers to Zilina in the first leg of their play-off, the Supercopa de Espana champions making nine changes to the starting XI that drew 1-1 with Barcelona at Camp Nou to end their trophy drought.
Preparing for their hosting of champions Barca in La Liga on Sunday, Bilbao coach Ernesto Valverde will be without Williams - who was withdrawn just eight minutes after coming on as a second-half substitute in Zilina.
Williams was withdrawn moments before Bilbao conceded an equaliser, before Zilina claimed the lead in the two-leg tie with a 94th-minute winner.
A Bilbao statement revealed the 21-year-old, who scored against Barcelona in the Copa del Rey final in May, was undergoing tests to determine the extent of the injury.