Zinedine Zidane apologised and said he wished Real Madrid's miserable season would end now after they were beaten by 19th-placed Rayo Vallecano on Sunday.
Madrid's response to Barcelona winning the title on Saturday night was to slip to a 1-0 defeat at Vallecas and fall 18 points behind La Liga's newly-crowned champions.
Zidane took over knowing Madrid's title challenge was all-but extinguished but the difference on Barca then was 12 points while catching Atletico Madrid, now nine ahead, seemed achievable.
Adri Embarba's penalty, given after consultation with VAR, was enough for Rayo, who move to within six points of survival, with three games left to play.
"Today we did nothing," Zidane said. "From minute one until the end, at all levels. Sometimes you cannot score but today we did not even create chances, did not play at all.
"We must be very angry. I am angry, because the image we gave off today was bad. I am responsible for this as well, not just the players. But we have to apologise for our performance today, all of us."
The gap widens between them and Barcelona, whose players had been dancing on the pitch at Camp Nou the night before and posing for photos with their children after wrapping up a fourth La Liga title in five years.
Asked if he would like the season to end now, Zidane said: "Yes, but we have to play these three games and do something different. We cannot end like this.
"It is about me as well, today what I did in the shape of the team, it didn't work at all. We must respect football and what this club represents."
Not since March 31 has anyone except Karim Benzema, out with a hamstring injury, scored for Madrid, who created precious few chances against a Rayo side that have conceded 62 goals this term. No side in the division has shipped more.
Zidane said last week that the league would be the club's first priority from August but, even with new signings and fresh motivation, it could prove difficult to flick the switch. Madrid's winning habit has long-been lost.
Rayo's last victory over Real at Vallecas was in 1997, by the same scoreline, and this time they were without their top scorer too, Raul de Tomas, who is on loan from Madrid and ineligible to face his parent club.
Zidane handed Gareth Bale another chance but he struggled to impress while Thibaut Courtois made his first start under the Frenchman, in ahead of Keylor Navas.
Rayo won their penalty in the 23rd minue as referee Pablo Gonzalez took advice from VAR before judging Jesus Vallejo to have hauled down Javi Guerra in the box. Embarba made no mistake.
Madrid wanted their own spot-kick when Mariano Diaz took a tumble from a corner but Gonzalez was unmoved, and the second half was surprisingly comfortable for Rayo.
Bale's free-kick was palmed away by Garcia while Zidane threw on Brahim Diaz, Lucas Vazquez and Isco in search of some inspiration. It never came.
Beneath Madrid, La Liga's last Champions League spot remains up for grabs after Valencia, Sevilla and Getafe all endured surprise defeats earlier on Sunday.
Valencia lost 1-0 at home to Eibar while Sevilla were beaten by the same scoreline away to struggling Girona, whose victory could prove crucial in their fight against relegation.
Both slips gave Getafe the opportunity to pull clear in the three-way race for fourth but they stumbled too, edged out 2-1 away to Real Sociedad.
Getafe stay ahead of Sevilla only on head-to-head, with Valencia three points behind and perhaps looking to the Europa League as their best hope of Champions League football next season.
Madrid, Spain | AFP