Athletic Club struck three times in the last 17 minutes as they came from 2-1 down to take a significant step towards the UEFA Europa League semi-finals.
It looked set to be Raúl González's night as he registered twice to overturn Fernando Llorente's opener midway through the first half, his second on the hour a sumptuous volley. Yet in a barnstorming finale, Llorente, Óscar de Marcos and Iker Muniain all scored and Klaas-Jan Huntelaar rattled an upright with a wonderful strike as it ended 4-2.
FC Schalke 04 coach Huub Stevens said on the eve of the first leg that he did not know what to expect from an Athletic side who have lurched from beautiful to ugly all season. The picture was little clearer in the early stages. They advanced with irresistible poise and purpose, especially on the right, yet there was little assurance defensively.
It was against the run of play, therefore, that Llorente broke the deadlock on 21 minutes. That it came from the right was no surprise, as De Marcos got in behind Christian Fuchs and cut the ball back to Markel Susaeta. His first-time shot was scuffed but Timo Hildebrand fumbled fatefully and Llorente pounced to prod in at the second attempt.
Schalke responded immediately as Raúl turned in Atsuto Uchida's cross at the near post. If that was not sufficient sign that, at 34, the fire still burns for the ex-Spain striker, then the sight of him eschewing celebrations to admonish Fuchs for his part in Llorente's goal was. Raúl almost had another before half-time but failed to get sufficient purchase on Julian Draxler's centre.
Llorente remained lively at the other end, bringing the best out of Joel Matip and Kyriakos Papadopoulous; it did not bode well for Mathias Schober, who replaced the injured Hildebrand at half-time – his first appearance in three years. The veteran was initially at ease, especially when Raúl lashed in a volley, but Llorente's equaliser, heading in a corner at the near post, changed everything.
Nine minutes from time De Marcos made it 3-2, adjusting well to turn in Schober's block from a Susaeta effort, and in added time Muniain rounded off a blistering counterattack. Athletic will start next Thursday's second leg as big favourites, even if they will be without the suspended Ander Iturraspe.