Barcelona lost against Valencia by 2-0 courtesy of a Jordi Alba own goal and a Maxi Gomez strike.
And Quique Setien's honeymoon at Barcelona is over.
The Spanish boss started his Barcelona career with a dominating home win against Granada and were tested away at Ibiza but he was finally brought back to earth as Valencia beat Barcelona by 2-0 at Mestalla courtesy of an own goal from Jordi Alba and a precise finish from Maxi Gomez. It could have been even more embarrassing, but a goal from Gabriel Paulista was disallowed and Marc Andre Ter Stegen saved a penalty for the visitors.
Barcelona dominated more than 70 percent of the ball, but found it hard to go through the Valencia defence as they were lacking the cutting edge. Valencia had an opportunity to punish them in the 12th minute as the hosts were gifted a penalty after Gerard Pique brought Gomez down in the box but ter Stegen managed to pull out a brilliant save to deny Gomez.
Valencia continued to trouble Barcelona with their counter-attacks but were kept at bay by Barcelona's German shot-stopper as Ter Stegen made some brilliant saves to keep the score 0-0 at the end of the second half.
Ansu Fati missed a golden opportunity to score at the beginning of the second half and Barcelona were punished at the other end as Gomez's shot deflected of Alba and went in.
Barcelona started to show some intent after Arturo Vidal was introduced but they kept on being wasteful as Lionel Messi squandered opportunities to score. And with Valencia's defence being sturdy, it looked impossible for Barcelona to score.
The game was killed off in the 77th minute as Gomez found space at the edge of the Barcelona box and put in a pinpoint finish as Ter Stegen helplessly looked at it as it went in. Barcelona could have been even more humiliated but Paulista's goal was disallowed because of a push on Sergio Busquets.
As the final whistle blew, it ensured Barcelona's first defeat at the Mestalla since the 2007-08 season and also put Barcelona's top spot in the La Liga points table in jeopardy as Real Madrid have a chance to surpass them even with a draw.
Barcelona's next game is on February 2 at home against Leavnte as the defending La Liga Champions will look to get back to their winning ways under their new manager.