Alex Remiro was shocked to see his name removed from Athletic's teamsheet for the start of the Liga season amid a dispute over his new contract.
Kepa Arrizabalaga's exit to Chelsea at the end of the Premier League transfer window left a big gap for Eduardo Berizzo's side, as the goalkeeper moved in a £72 million (€80m/$92m) deal.
The 23-year-old Remiro is seen as a natural replacement, particularly after Kepa's former understudy Iago Herrerin has been ruled out through injury, having performed heroically on loan at Huesca last season in a campaign that saw the team promoted to the Spanish top flight.