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their hosting of champions Barca in La Liga on Sunday, Bilbao coach Ernesto Valverde will be without Williams - who was withdrawn just eight minutes after coming on as a second-half substitute in Zilina.
Williams was withdrawn moments before Bilbao conceded an equaliser, before Zilina claimed the lead in the two-leg tie with a 94th-minute winner.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.
