Athletic Club will compete in their first European quarter-final tie for 35 years after following up their first-leg victory against Manchester United FC with a 2-1 win at San Mamés.
Marcelo Bielsa's side earned high praise after leaving Old Trafford with a 3-2 triumph and they did not disappoint here either. Fernando Llorente and Óscar de Marcos scored the goals to cap a similarly energetic display against the Premier League leaders, who reduced their arrears through Wayne Rooney late on.
Spurred on by a full congregation at the ground known as La Catedral, Athletic nearly extended their aggregate advantage as early as the 13th minute, Iker Muniain striking a post following neat build-up play involving Javi Martínez and Llorente. Muniain, a recent Spain debutant who netted Athletic's third last week, could only watch as De Marcos stepped ahead of him to smash the rebound over the bar.
The visitors, who had lost just one of their previous four European away games this season, had only a blocked Ashley Young shot to show for their efforts. They were under pressure for most of the first half and fell behind in the 23rd minute. Seeking out Llorente's run into the area, Fernando Amorebieta struck a searching pass which the striker met first time, unleashing a sumptuous volley which flew past David de Gea.
Ryan Giggs's header was then deflected over by Jon Aurtenetxe, while after the restart Andoni Iraola struck wide following a dizzying run into the opposition area. It was only a matter of time before a second eventually arrived for the 1976/77 UEFA Cup finalists. De Marcos got it, striking past De Gea after Chris Smalling had deflected away from the head of substitute Gaizka Toquero.
A spectacular long-range drive from Rooney ten minutes before the end left Athletic goalkeeper Gorka Iraizoz with no chance. The hosts, though, were not to be denied a second victory in this city against United to add to a 5-3 home triumph over Sir Matt Busby's side 55 years ago. And this time, victory sent them through.