Atletico Madrid's hopes of finishing second in La Liga this season have taken a hit, with Espanyol recording a 2-0 victory at the Wanda Metropolitano on Sunday afternoon.
Oscar Melendo and Leo Baptistao scored the goals as Diego Simeone's side lost for the first time in the league on home soil this season.
Atletico remain second in the table behind Barcelona, but Real Madrid are just four points behind with two games in hand - one of which is against Barcelona on Sunday night.
The capital giants overcame Arsenal on Thursday night to book their spot in the Europa League final, but suffered a hangover in Madrid as they conceded their first home goals in any competition since January 20.
Vitolo had Atletico's best chance of what was a cagey first period, but the Spain international could only fire wide of the post from a promising position in the final third of the field.
Espanyol grew into the latter stages of the first 45 minutes, and took the lead early in the second when Melendo was first to react to a loose ball inside the box, and he found a route into the back of the net.
Atletico goalkeeper Jan Oblak made a smart save to keep out a Baptistao effort in the 66th minute, but the stopper was beaten by the Brazilian forward 11 minutes later with a strike that flew into the bottom corner of the net.
Antoine Griezmann was left on the bench for the home side while Diego Costa missed out altogether, and their replacements Fernando Torres and Kevin Gameiro struggled to upset a stern Espanyol back four.
Next up for Simeone's side is a trip to Getafe on Saturday afternoon, while Espanyol host Malaga next Sunday.
ATLETICO (5-3-2): Oblak; Vrsaljko, Gimenez, Savic, Lucas, Luis (Gabi 65'); Koke (Saul 46'), Thomas, Vitolo (Sane 26') Torres, Gameiro
ESPANYOL (4-4-2): P.Lopez; J.Lopez, D.Lopez, Naldo, Vila; Melendo (Garcia 78'), C.Sanchez, V.Sanchez, Darder (Roca 72); Baptistao, Moreno (Jurado 83')
