Barcelona stumbled in the Spanish title race with a 1-1 draw against rivals Espanyol in a bad-tempered Catalan derby on Saturday, levelling Real Madrid at the top of La Liga.
Xavi's side threw away the two point advantage they had earned before the World Cup break, with Joselu's penalty pegging Barcelona back after Marcos Alonso's opener.
Both teams finished with 10 men as Jordi Alba and Vinicius Souza were sent off, with referee Mateu Lahoz allowing the game to spiral out of control at Camp Nou.
The teams were at loggerheads before a ball as kicked because Barcelona started Robert Lewandowski, who had been banned before a late court ruling allowed him to play.
The forward, due to miss three league matches, was only allowed to play thanks to a controversial decision announced on Friday, suspending his punishment.
It greatly angered Espanyol, whose president and directors boycotted the match, while Barca coach Xavi admitted his team had prepared all week expecting to be without the division's top goalscorer.
The Spanish football federation said in a statement on Saturday they could not override the court's decision.
Lewandowski was not at his best but Barcelona took the lead after just seven minutes with Alonso capitalising on shoddy set-piece defending from Espanyol to head home.
The former Chelsea defender, deployed as a centre-back, should have doubled his tally but sent Alba's cross wide from point-blank range.
Espanyol's only chance of the first half came when Nico Melamed had a shot deflected wide of Marc-Andre ter Stegen's far post.
The visitors, 16th, struggled to create much more but won a penalty after Alonso tangled with Joselu in the area, and the forward dispatched it down the middle.
Lahoz, racking up the bookings, sent off Alba for two in quick succession, before dismissing both Souza for a foul and Leandro Cabrera for a clash with Lewandowski seconds later.
However he cancelled the latter dismissal after watching the incident again with VAR, and Barcelona could not find a winner in the nine minutes added on.
Barca coach Xavi also received a booking from Lahoz for complaining from the sidelines late on, and the official left the stadium to jeers and whistles from the home fans.
Barcelona and Real Madrid, who beat Real Valladolid on Friday, are both on 38 points from 15 games, leaving the title race neck and neck ahead of the new year.