Barcelona fell apart as Levante scored three times in seven second-half minutes to claim a dramatic 3-1 La Liga victory. (More Football News)
Lionel Messi, who returned to the Argentina squad this week, made it six goals in his last five games with a first-half penalty that appeared to have leaders Barca on course to extend a seven-match winning streak in all competitions.
But after Luis Suarez went off injured, an astonishing spell saw Jose Campana, Borja Mayoral and Nemanja Radoja all score as the match was turned on its head.
Barca's defeat means Real Madrid, who face Real Betis later on Saturday, have the chance to go top of the table with a victory.
After a quiet start to the contest, Antoine Griezmann saw a right-footed effort saved by the outstretched leg of Levante keeper Aitor Fernandez, Messi's through ball having created the opportunity.
Barca's breakthrough arrived seven minutes before the break, a slick passing move ending when Arthur found Nelson Semedo, who was hacked down by Jorge Miramon in the box.
Messi stepped up and comfortably sent Fernandez the wrong way from 12 yards, finding the top-right corner.
He almost had a second with half-time approaching, only for a combination of Fernandez and Miramon to deny him from close range, while Barca were forced to replace an injured Suarez after the striker could not run off an earlier knock.
Levante did not produce a shot on target in the first hour, but levelled the match when a poor Gerard Pique clearance led to Mayoral and Jose Luis Morales combining to set up Campana, who confidently beat Marc-Andre ter Stegen from just inside the area.
Just two minutes later, Mayoral collected a pass from Campana and curled an excellent 20-yard strike beyond Ter Stegen, who got a hand on it.
An astonishing sequence concluded with Levante's third after 68 minutes, with Clement Lenglet's headed clearance volleyed in by Radoja from 18 yards, courtesy of a big deflection off substitute Sergio Busquets.
VAR ruled out a second goal for Messi due to offside against Griezmann in the build-up and that was as close as Barca came to producing a fightback, despite the arrival of Ansu Fati from the bench.
What does it mean? Another away loss brings Barca back down to earth
Barca had started to hit top gear during their seven-match winning streak but could now fall behind rivals Madrid.
They have suffered three league defeats in only six away games this season and will also hope the injury to Suarez does not make this collapse even more costly to their title hopes.
Campana crucial in comeback
Campana was superb for Levante, scoring the equaliser, setting up Mayoral's strike and creating three chances for his team-mates in an influential display.
Griezmann quiet in defeat
The injury to Suarez afforded Griezmann the chance to play more centrally, but he struggled to make an impact as his mixed start to life at Barca continued.
He had a first-half chance saved and poorly found the side netting with another opening before being spared by the offside flag. He did not create a single chance for his team-mates either.
What's next?
Barca look to bounce back when they host Slavia Prague in Champions League business on Tuesday before a return to LaLiga action against Celta Vigo on Saturday, a match which is also at Camp Nou. Levante, meanwhile, are away to Athletic Bilbao on November 10.
