Barcelona stunned Real Madrid with a 4-0 victory on Sunday as Pierre-Emerick Aubameyang scored twice in a Clasico demolition at the Santiago Bernabeu.
The match was billed as a test of Barca's progress under Xavi Hernandez and they passed with flying colours, a humiliation of their fiercest rivals suggesting they are primed to challenge again for La Liga next season.
And while the result might have little bearing on the title race this term, a defeat of this magnitude, at home, and against Barcelona, will cause serious reverberations at Real Madrid.
Questions will be asked about Carlo Ancelotti's future, with Madrid outplayed tactically and technically by Xavi's Barca, who were faster, slicker and, perhaps most worryingly, could easily have won by more.
Madrid were admittedly without the injured Karim Benzema and Ferland Mendy while there could have been a degree of complacency, given they kicked off nine points clear at the top of the table after Sevilla were held to a goalless draw by Real Sociedad.
But none of that will excuse a loss as dramatic as this one, the only relief now that a resurgent Barcelona are still 12 points behind, albeit with a game in hand.
When Barca were beaten by Real Madrid in the Spanish Super Cup in January, the Catalans were criticised for celebrating the manner of their narrow defeat.
"We are getting closer," said Gerard Pique.
After five consecutive losses to Madrid, a win of any kind was the next step for Barca but a hammering like this could be transformative, delivering a huge boost to confidence, vindication of Xavi's project and optimism for next season all in one fell swoop.
'We are back'
Shortly after the final whistle here, Pique tweeted: "We are back."
Eder Militao clattered Pedri in the opening minute and that was about as close as Real Madrid got to him all game. Fede Valverde had an early shot tipped wide but Barcelona settled and by the 23rd minute, their fans up in the top corner were cheering every pass.
Soon, the chances started coming as Ferran Torres pulled back for Aubameyang but he scuffed straight at Thibaut Courtois, who then had to palm wide a curling effort from Ousmane Dembele.
Pedri scooped a delightful ball through for Torres, only for the sliding Casemiro to block but Barca's dominance was growing and in the 29th minute they scored, Dembele racing round the outside of Nacho Fernandez and crossing for Aubameyang to head in.
Vinicius Junior might have changed the game if he had converted after being sent through but a heavy touch allowed Marc-Andre ter Stegen to save.
Instead, Barcelona doubled their lead when Ronald Araujo headed in from a corner before half-time and after it, the humiliation began. Within seconds of the restart, Torres was clear and while he shot wide, another chance came a minute later.
David Alaba and Militao both committed themselves to sliding tackles and both missed, Aubameyang executing a superb flicked pass to Torres, who this time made no mistake.
The Real Madrid fans had whistled at half-time but they were not so much frustrated now as stunned, their team looking lost, flat and beaten.
Worse was to come, as Pique's ball over the top allowed Aubameyang to scoop in a brilliant finish for a fourth in the 51st minute. Madrid thought they were spared by the offside flag but VAR intervened and the goal stood. Barca celebrated, the substitutes joining in on the touchline.
Aubameyang, Torres and Dembele could all have furthered the embarrassment for Madrid, the latter poking wide after skipping in behind and holding off Militao.
By then, Aubameyang had gone off, the victory already complete and the stadium quickly emptying.