Atletico Madrid have suffered a blow in their bid for a top-two finish in La Liga as they fell to a 3-0 defeat at Real Sociedad on Thursday evening.
Diego Simeone's charges, who boast one of the best defences in the Spanish top flight, were picked apart by the inspired Basques at the Anoeta Stadium.
The deadlock was broken on 27 minutes when Adnan Januzaj cut the ball back for Willian Jose, who rifled it into the back of the net off the base of the left post from 12 yards out.
An erroneous offside decision denied Atletico a clear goalscoring opportunity on 41 minutes, a long ball over the top destined for Kevin Gameiro being flagged, but the hosts were worthy of being ahead come the break.
Jose then turned provider in the 80th minute, his fine touch freeing substitute Juanmi for a neat dinked finish over Atleti goalkeeper Jan Oblak.
Juanmi rounded off the victory with a well-taken header two minutes into stoppage time, nodding in his side's third from Alberto de la Bella's pinpoint cross to put them 11th in the standings.
Atletico, meanwhile, now sit just three points ahead of bitter rivals Real Madrid in second, and 12 points behind leaders Barcelona with just five games left to play.
REAL SOCIEDAD (4-3-3): Rulli; Elustondo, Navas, Moreno, de la Bella; Canales, Illarramendi, Pardo (Zurutuza 65'); Januzaj, Jose (Bautista), Oyarzabal (Juanmi 72')
ATLETICO MADRID (4-4-2): Oblak; Juanfran (Vitolo 54'), Savic, Godín, Vrsaljko; Correa (Torres 45'), Niguez, Thomas (Fernandez 75'), Koke; Griezmann, Gameiro