Atletico Madrid piled misery on Barcelona by beating them for the first time in 10 years, and put nine points between themselves and Ronald Koeman's side on the LaLiga table. This was the first time Diego Simeone beat Barcelona in the league, with Atletico ending a 20-game winless run against the Catalans in the Spanish top-flight.
The defeat also saw Barcelona slump to a new low in LaLiga - the Catalan giants have picked up just 11 points from their first eight LaLiga games this season - their worst tally since 1991-92.
Yannick Carrasco capitalised on an error from Marc-Andre ter Stegen, but the German's mistake is unlikely to be what the game will be known for.
Koeman's side have been exceptionally poor this campaign, winning just one of their last five LaLiga games. However, the Dutchman might find some solace in the fact that the last time Barca started this poorly in 1991-91, they did go on to be crowned champions as they finished one point ahead of Real Madrid.
Things went from bad to worse for the Catalans after Gerard Pique was forced off with a knee injury as the club's injury crisis deepened. Sport claim Pique could face a six-month lay-off, adding to the growing list of absentees for Barca, who are already without Ansu Fati and Samuel Umtiti, while Sergi Roberto also hobbled off in Saturday's 1-0 defeat.
Speaking after the game, Koeman said, "We played well in the first half but it cannot be that a team like Barcelona concede a goal like that so late in the first half. The players are competing well but we want better results. We had our chances to get back into the game but it is always tough against an Atletico side that defend so well."
The Barca boss will be hoping to see his side bounce back in the Champions League on Tuesday as they take on Dynamo Kyiv, with the Catalans winning all three of their group games in the competition to date.