Barcelona lost at home for the second time in four days as Lucas Perez struck to seal a surprise 1-0 victory for LaLiga strugglers Cadiz.
Perez missed the best chance of a dull first half when blazing wide from 12 yards out, but the former Arsenal forward atoned to prod home the game's only goal after 47 minutes.
Jeremias Ledesma pulled off a string of fine saves to stem Barca's comeback attempts, as Xavi saw his side's 15-match unbeaten run in the league come to a shuddering halt.
Having crashed out of the Europa League to Eintracht Frankfurt on Thursday, Barca's slim LaLiga title hopes are surely now over, and they sit only three points above fifth-placed Real Betis.
Despite a boycott from some fans creating a flat atmosphere at Camp Nou, Barca made a bright start – Ousmane Dembele and Ferran Torres forcing Ledesma into a double save.
Cadiz soon settled, and missed the first glaring opportunity of the match after 27 minutes, Perez inexplicably side-footing wide with the goal gaping.
Dembele shot tamely at Ledesma at the other end and Perez made Barca pay after the restart, making no mistake as he nudged in from close range after Marc-Andre ter Stegen had made a fine save.
Ledesma again thwarted Dembele 20 minutes later, though Barca were fortunate that Alex Fernandez and Ruben Sobrino missed great chances.
Ledesma denied Luuk de Jong and turned away Eric Garcia's strike before making his best save of the match, reacting brilliantly to parry Pierre-Emerick Aubameyang's volley as Barca fell to a demoralising defeat.
What does it mean? Limp display surely ends title hopes
Xavi's team came into this match on the back of seven consecutive wins in LaLiga, and could have won eight successive league matches for the first time since January 2019, under Ernesto Valverde.
However, relegation-threatened Cadiz – who are now out of the bottom three – punished their hosts, claiming their first ever win at Camp Nou in LaLiga.
Cadiz becoming Barca's bogey team
Though this was Cadiz's first LaLiga win away at Barca, the Andalusian side have not lost any of their last four top-flight matches against the Blaugrana.
Meanwhile, Perez has scored four league goals against Barca for Cadiz, only scoring more against Valencia (six). Three of these strikes have come at Camp Nou.
Barca miss defensive duo
Although Barca produced an attacking display devoid of inspiration, they also sorely missed first-choice defensive pair Ronald Araujo and Gerard Pique.
Barca were unbeaten in the three previous games in which Eric Garcia had partnered Clement Lenglet, but the pair were unable to thwart Perez.
Key Opta Facts
- Barca have lost consecutive games at home in all competitions for the first time since April 2003
- Barca have kept just nine clean sheets in LaLiga this season after 31 games played. Their worst tally in the 21st century is 10 in 2012-13.
- Dembele had seven shots, matching his highest tally in a single game this season in all competitions (seven against Linares in Copa del Rey).
- Barca have conceded 32 goals after 31 games in LaLiga, their worst tally at this stage in the competition since the 33 they had conceded in the 2012-13 campaign.
- Ledesma is the first goalkeeper to make six saves in LaLiga this season without conceding a goal.
Barca are back in action when they travel to Real Sociedad in La Liga on Thursday, while Cadiz host Athletic Bilbao earlier that day.