Barcelona's title defence was derailed as Villarreal romped to a sensational 5-3 victory in La Liga on Saturday with three late goals, and coach Xavi Hernandez said he was responsible for the Catalans' defeat.
After Real Madrid moved two points clear of Girona at the top of the league with a late 2-1 win at Las Palmas, the pressure was firmly on Xavi Hernandez's defending champions in third.
In a see-saw match Gerard Moreno and Ilias Akhomach put Villarreal two goals ahead before Barcelona battled back.
Ilkay Gundogan and Pedri struck before Eric Bailly headed into his own net to give the hosts the lead.
However Goncalo Guedes fired home in the 84th minute before stoppage-time strikes from Alexander Sorloth and Jose Luis Morales left Barcelona 10 points adrift of rivals Madrid.
"I understand that the players (say) they are responsible, but I am the responsible one," Xavi told DAZN.
"We have to change the dynamic, it makes La Liga very hard for us."
The coach added: "It's a tough blow, the team's morale is very low (but) the club has come out of worse situations."
Alex Baena and Moreno had goals disallowed for Villarreal before the latter broke the deadlock, finishing well from Sorloth's cut-back.
As the players trudged in for half-time Barcelona were whistled by disgruntled supporters at their temporary home at the Olympic Stadium.
Xavi made a triple change at the break, throwing on Joao Cancelo, Pedri, and 17-year-old defender Pau Cubarsi.
It fired the team up, but they conceded a foolish second goal after a bad Cancelo mistake allowed Akhomach to gallop in, round Inaki Pena and fire home.
Undeterred, Barcelona fought back.
Gundogan finished superbly from the edge of the box after an hour, Pedri drove home eight minutes later to level and Bailly headed Gundogan's free kick into his own net.
However Barcelona's defence, a far cry from the watertight back-line which led them to the title last season, was pulled apart again.
Sorloth fed winger Guedes, who flashed a strike past Pena and into the far corner.
Barcelona were awarded a penalty in the 90th minute when Santi Comesana blocked Gundogan's cross with his elbow but the referee cancelled it after a VAR review, leaving the hosts furious.
Xavi yelled into a television camera that the decision to revoke the penalty was "a disgrace".
"They will punish me, you analyse it, I don't want to generate more controversy," he later told DAZN.
Worse was to come, with Sorloth finishing from close range to put Villarreal ahead and Morales rubbed salt in the wound with a late fifth, with Barcelona in total disarray.
It was Villarreal's first win in five games in all competitions and their coach Marcelino's first ever against Barcelona in 21 matches.
"It's turning out to be a tough season and the fans deserved something like this," said Moreno.
Motivated bench
Earlier Aurelien Tchouameni's towering header earned Real Madrid a late victory at Las Palmas to send them top.
Las Palmas took the lead through Javier Munoz early in the second half but Madrid came back with Vinicius Junior levelling before substitute Tchouameni's winner, on his birthday.
"I look at the bench and I have chances to change the dynamic," the Italian coach told reporters.
"It's a tool that we have, with such a motivated bench, they bring a lot when they come on."
Madrid were without leading goalscorer Jude Bellingham, suspended.
Promoted Las Palmas, eighth, have exceeded expectations under former Barcelona reserves coach Francisco Garcia Pimienta, and for large periods they gave Madrid as good as they got.
It was a tight clash between the division's best two defences but the stalemate was broken early in the second half.
Munoz finished a neat counter-attack before Vinicius levelled after a fine Eduardo Camavinga pass.
Real coach Carlo Ancelotti, chasing a winner, sent on Turkish attacker Arda Guler for his La Liga debut and match-winner Tchouameni.
The French midfielder netted only his second goal for the club with a superb header from Toni Kroos' corner with six minutes remaining.
Madrid have been taking full advantage of dead ball situations, with this just the latest in a string of goals from corners they have scored this season.
"At set pieces we're very dangerous because we have very good takers and very good finishers," said Ancelotti.
