Atletico Madrid's top-four chances suffered another blow as they slumped to a surprise 1-0 defeat at home to Levante, who became the first away team to win two La Liga games at the Wanda Metropolitano.
Diego Simeone's men were overtaken in fourth by Barcelona 10 days ago and the champions will trail them by three points if the Blaugrana go on to win their game in hand.
Atletico remained level at half-time despite an underwhelming display, but they were punished in the 54th minute by Gonzalo Melero's crisp finish.
A penalty award in favour of Atletico was then reversed soon after and, although Simeone threw attacking players on towards the end, they could not salvage a point.
Atletico offered precious little in a first half that Levante dominated for spells with 60 per cent possession.
The hosts were indebted to Jan Oblak as Levante looked destined to take the lead in the 22nd minute, the goalkeeper making a vital one-on-one save to deny Jorge de Frutos after Stefan Savic's miscued header.
Levante deservedly went ahead early in the second half, De Frutos teeing up Melero for a first-time finish that beat Oblak at his near post.
Atletico thought they had the chance to level from the spot when Geoffrey Kondogbia's shot was blocked by an arm, but referee Jose Luis Munuera Montero overturned his decision due to Marcos Llorente straying offside in the build-up.
A chaotic end saw Angel Correa have an equalizer disallowed for an apparent foul on Martin Caceres by Jose Gimenez, before Mickael Malsa struck the crossbar for Levante from 40 yards – not that it mattered as the visitors clung on for a massive win.