LaLiga champions Atletico Madrid fell to a shock 1-0 defeat on Wednesday at home to basement club Levante, who picked up only their second win of the season.
Gonzalo Melero's goal in the second half inflicted a sixth defeat in 10 league matches on Atletico, deepening their problems a week before they host Manchester United in a Champions League last-16 first leg.
Atletico had pulled off stunning comeback victories at home against Valencia and Getafe in the last month and thought they had grabbed an equaliser when Angel Correa netted with a spectacular overhead kick in stoppage time.
But the goal was ruled out for a foul by Jose Gimenez on Martin Caceres and Correa was shown a yellow card for his angry reaction to the decision.
Levante's Mickael Malsa almost scored a second for the visitors with a spectacular effort from near the halfway line which hit the crossbar.
Atletico then came within inches of snatching a last-gasp leveller when goalkeeper Jan Oblak came up to contest a set-piece and headed just wide of the far post.
Diego Simeone's side missed the chance to overtake Barcelona in fourth spot and were left fifth in the standings on 39 points. Levante stayed bottom of the table but moved on to 14 points, 10 from escaping the relegation zone.