Alex Berenguer‘s scintillating strike after a Casemiro mistake was enough to seal a shock 1-0 victory at San Mames and send Athletic through to the semi-finals.
With Barcelona, Atletico Madrid and Sevilla already out, Madrid were firm favourites to win the Copa del Rey while in La Liga, they are in the driving seat too, sitting four points ahead of Sevilla at the top of the table.
But it will be Athletic that join Real Betis, Valencia and Rayo Vallecano in the last four and while Betis are flying high in the league, all four teams will have genuine hopes now of lifting the trophy.
For Athletic, it would be particularly special, coming after they were beaten in two finals in two weeks last year, the first a postponed game from 2020 against Basque rivals Real Sociedad, and the second at the hands of Barcelona. They defeated a Real Madrid team that was almost at full-strength and certainly the best Carlo Ancelotti had at his disposal, even if the visitors dearly missed Karim Benzema, who is still recovering from injury.
Without Benzema, Madrid lacked any real threat up front and it was a daunting reminder for Ancelotti of his lack of quality options to back up the Frenchman when he needs them.
The match was intense and compelling but low on chances, with neither team able to carve out any golden opportunities, even if Athletic were the more aggressive overall.
When the decisive moment came, it came from a mistake as Casemiro’s sloppy pass was cut out by Mikel Vesga, who quickly fed into Berenguer.
He still had work to do but made the space with a sharp turn away from Nacho Fernandez, before burying a superb shot past Thibaut Courtois and into the far corner.