Carlo Ancelotti apologised for Real Madrid's shocking 4-0 capitulation to Barcelona at the Santiago Bernabeu, admitting: "It's all gone wrong."
Madrid, who still hold a nine-point lead over second-placed Sevilla in LaLiga, were mauled by a resurgent Barcelona as Xavi's first taste of this LaLiga clash as a coach ended in glorious triumph for the visitors.
Barcelona are nowhere near being in the hunt for the league title this season, but this was a fifth consecutive win in the competition, and in four of those games they have hit four goals. They are now third and pushing to finish second.
Since his November appointment, Xavi's Barcelona have taken 37 points from 16 games in LaLiga, while Madrid have 39 from 17 outings.
These great rivals are going toe to toe again in the second half of the season, and it is little wonder Madrid want to sign Kylian Mbappe to strengthen their ranks for next term, given momentum is suddenly all with Barcelona.
Ancelotti nudged Luka Modric into more of an attacking role, the 36-year-old midfielder deployed as a false nine in the absence of a genuine number nine in Karim Benzema, who is injured and was sorely missed.
The head coach said that was intended as a means of taking control of the ball and looking to press high, with Modric primed to bring others into the game.
"And it hasn't worked out," Ancelotti said. "When they advanced, we lost control. They hurt us. It was not a good night, we are sorry for the fans, but we have to look forward. We have an advantage, we have to rest and come back.
"I tried to push up and it hasn't come off, my fault. It's hard because it's a Clasico, we're very sorry, it's a blow, we've lost a battle, but we have an advantage, we have to be calm, calm and recover. We don't have to make a drama out of this match. We're sorry. It's all gone wrong, we have to forget it and look forward."
With four defeats in six editions of El Clasico as a coach, Ancelotti has found it difficult to manage this fixture.
"I've failed in this game, but I'm not making a big deal out of it," he said.
This is Ancelotti's second stint in charge of Los Blancos, after he was lured away from Everton ahead of this season. His Madrid side won 2-1 at Camp Nou in October, prior to Xavi's arrival, and then beat Barcelona 3-2 after extra time in the Supercopa semi-finals in January.
Former Barca playmaker Xavi has increasingly brought a serenity to affairs at a club where there was considerable chaos earlier in the campaign.
Now it will be Ancelotti's task to ensure Madrid are not left scarred by a defeat in which Pierre-Emerick Aubameyang ran the hosts ragged, scoring twice and teeing up another goal for Ferran Torres. Ronald Araujo also beat Thibaut Courtois, whose goal was peppered with shots as Madrid defended dreadfully.
Xavi became the third Barcelona coach to win his first LaLiga Clasico by four or more goals, after Ferdinand Daucik in 1951 (7-2) and Helenio Herrera in 1959 (4-0).
Ancelotti is optimistic Madrid's supporters will allow him and the team a blip, even one of such scale against the club's greatest enemies.
"They understood that it was not a good night," Ancelotti said. "We don't know what will happen in the coming months. We can recover and win the next game. I don't think this will affect the team."