Diego Simeone's men had previously won every league match at home this season, but went down to Sociedad at the Vicente Calderon, meanwhile there was wins for Rayo and Betis
Real Betis moved to within a point of the Champions League places in La Liga with a 2-1 victory over Osasuna on Friday evening.
Kike Sola and Oier went close with long range strikes as Osasuna made the brighter start, but it was the hosts who edged ahead against the run of play. Joel Campbell stood a cross into the box and Jorge Molina rose high to power a header into the top corner.
Jose Luis Mendilibar's men eventually clawed a goal back 73 minutes in when Francisco Silva found the bottom corner from 12 yards out. However, their lead only lasted six minutes.
Ruben Castro ran in behind the Osasuna defence and coolly converted past the oncoming Andres Fernandez.
Pepe Mel's men held on for the victory, which sees them on the brink of the top four.
RAYO 2-0 ESPANYOL
A 2-0 home victory over Espanyol on Saturday left Rayo within three points of the Champions Leauge places in the Spanish Primera Division.
The hosts made their intentions known early, and took the lead after just nine minutes. Leo Baptistao displayed rapid pace to burst into the box before reversing a cross into the box for Chori Dominguez, who unconventionally finished with his knee.
Sergio Garcia had a couple of opportunities to equalise for Espanyol in the first period, but he put a shot wide from the edge of the area and struck a weak shot into the arms of Ruben.
Francisco Casilla was on form for the visitors and kept his side in with a shout with a couple of good saves after the break. However, he was the guilty part for Rayo's second goal.
The Espanyol 'keeper rashly came off his line which allowed Piti to run through on goal round him before slotting home, ensuring the home side took all three points.
VALLADOLID 1-1 MALAGA
A goal from either side in the first half ensured the points were shared as Malaga could only manage a 1-1 draw against Valladolid on Saturday evening.
Manuel Pellegrini opted to shuffle the pack ahead of his side's Champions League encounter with Porto on Wednesday, with Joaquin and Isco both rested. Despite the changes, they looked comfortable early on and took the lead after just eight minutes. Lucas Piazon floated a deep free kick to the back post and an unmarked Martin Demichelis headed in from a few yards out.
Malaga looked settled on the ball, but their inability to find a second goal eventually punished them just before half time when Valladolid drew level. Manucho latched on to a cross from Alvaro Rubio to head past Willy Caballero, who was rooted to the spot.
The former Manchester United striker had a couple of close range attempts that went begging for the hosts, but poor conditions meant the match lacked flow. Both sides looked happy to settle for the draw in the end.
MALLORCA 2-1 SEVILLA
A double from Alejandro Alfaro gave Mallorca a boost in their battle against the drop as the Islanders defeated Sevilla 2-1 in La Liga.
Alfaro netted is first league goal of the season in the win over Granada last week, and continued the run against Unai Emery's men 16 minutes in when he pounced on a save from Antonio Beto to slot home following a Giovani dos Santos free kick.
They could have extended their lead 10 minutes later through a Fernando Tissone free kick, but his attempt cannoned off the crossbar.
Instead, it was Sevilla who managed to equalise in the second half. Ivan Rakitic fizzed the ball into the feet of Alvaro Negredo, who showed composure to turn the ball into the bottom left corner.
However, Mallorca response was almost immediate, as the regained their lead five minutes later. Dos Santos headed the ball off the bar from the edge of the area and Alfaro was on hand again to smash home from the rebound, ensuring consecutive wins for Gregorio Manzano's outfit.
ATHLETIC 1-0 VALENCIA
Iker Muniain's first league goal of the season gave Athletic Bilbao a narrow 1-0 victory over Valencia at San Mames on Sunday morning.
Gorka Iraizoz and Vicente Guaita were not called into action too many times in the opening 45 minutes, with Ibai Gomez coming the closest to scoring when his free kick bounced off the woodwork on the brink of half time.
Muniain replaced Jon Aurtenetxe in the second half and almost made an instant impact. He showed superb skill to skip past two challenges, but his final shot trickled into the arms of Guaita. However, he made amends with 10 minutes to go when he latched on to a loose ball 12 yards out to lash a fantastic strike into the top right corner.
Roberto Soldado should have levelled the match when he received the ball three yards out, but somehow managed to clear his shot over the bar.
The result gives Marcelo Bielsa's men an eight-point gap above the dropzone, and leaves Valencia two points adrift of the Champions League spots.
LEVANTE 0-0 GETAFE
A lack of cutting edge from both sides saw Levante and Getafe play out a goalless 0-0 stalemate in the Spanish Primera Division.
Both Gustavo Munua and Miguel Moya denied the opposition with decent strikes from range in the first half, as both sides probed for the opener. Ivan Lopez then came extremely close to edging his side ahead, but his 20-yard strike struck the crossbar.
Levante dominated possession in the second half, but were unable to convert their control of the ball into meaningful chances.
Vicente Iborra nearly stole all three points for the hosts in the dying minutes, but his shot from outside the area once again saw Levante hit the woodwork, ensuring the points were shared.
ATLETICO 0-1 REAL SOCIEDAD
Atletico Madrid's perfect home record in the Spanish Primera Division ended on Sunday evening as they went down 1-0 to Real Sociedad at the Vicente Calderon.
Arda Turan, Cristian Rodriguez and Koke all tested their luck in the opening stages with strikes from the edge of the area, but each effort whistled by the post.
Turan was lucky to remain on the park in the second half when the referee failed to brandish a second yellow card after the Turk rashly slid on Antoine Griezmann.
The hosts improved after the break but it was Sociedad who took a shock lead eight minutes after the restart. Griezmann slid a pass through to Xabi Prieto who burst forward before lashing the ball under Thibaut Courtois.
The hosts failed to muster up any kind of threat to to Claudio Bravo's goal for the remainder of the match, and the result moves them down into third place behind Real Madrid in the table.