FC Barcelona suffered its second defeat of the season when it was beaten 1-0 by Real Sociedad on Sunday night.
The result leaves Barca six points clear of Real Madrid at the top of La Liga, but Madrid has a game in hand.
Sheraldo Becker's first-time finish into the corner of the net was enough to give Real Sociedad all three points, which was a reward for the San Sebastian-based side's best performance of the season, while Barcelona was below its best.
Hansi Flick's team was rocked with the loss of Lamine Yamal before kickoff, with the club announcing he had suffered an ankle injury, while Frenkie de Jong also had to leave the match injured.
Barcelona struggled to repeat the high-press that has served it so well this season, leaving its high defensive line vulnerable to the home side, who attacked effectively with Becker, Take Kubo and Mikel Oyarzabal.
Real Sociedad was also disciplined and committed in defense, and it says much of its display that although Robert Lewandowski saw a first-half effort ruled out for the narrowest of offsides, Barcelona failed to have a legal effort on target all game.
On Saturday, Vinicius Jr's hat-trick saw Real Madrid back to winning ways with a 4-0 win at home to Osasuna, with Jude Bellingham scoring the other goal.
Worryingly for Real Madrid, the win came at a heavy cost with central defender Eder Militao suffering a season-ending cruciate ligament tear, while full back Lucas Vazquez and forward Rodrygo suffered muscle injuries.
Villarreal registered a 3-0 win at home to Alaves, which was given extra sheen by two goals in the last ten minutes as the home side turned on the style in the second half.
Ilias Akhomach opened the scoring with a turn and left-footed shot in the 38th minute, before he fell victim to a torn knee ligament.
Dani Parejo's 81st-minute penalty and Santi Comesana's finish from another swift break rounded off a convincing win.
Julian Alvarez's second-half goal on an assist from Giuliano Simeone gave Atletico Madrid a 1-0 win in Mallorca.
Mallorca will be frustrated at its defending in the goal and also after failing to take any of the several chances it created in the game, with Jan Oblak again impressing in the Atletico goal.
Real Betis twice came back from behind to take a point in a 2-2 draw with Celta, thanks to Marc Bartra's 95th-minute diving header.
Javi Rodriguez fired Celta ahead in the 13th minute, but loanee Vitor Roque leveled five minutes from halftime when he side-footed home Johnny Cardoso's pass.
An unmarked Anastasios Douvikas put Celta back ahead at the far post with eight minutes left to play, but Bartra saved a point at the death for Betis.
Gorka Guruzeta's acrobatic 94th-minute finish saved a point for Athletic Bilbao away to Valladolid just when it looked as if Raul Moro's 79th-minute header was going to give the home side its second home win of the season.
Neither side created many clear chances in the game, with Athletic looking tired after Thursday's UEFA Europa League visit to Bulgaria.
Yangel Herrera's 42nd-minute header gave Girona an important win away to Getafe, who has only got one triumph all season and could drop into the bottom three if Valencia and Espanyol win their games in hand, after the weekend clash between the two sides was postponed.
Miguel de la Fuente's 81st-minute penalty gave Leganes three vital points in a 1-0 win at home to Sevilla, who ended up with 10 men after Lucien Agoume was sent off after committing the spot kick that decided a tactical game.
On Friday night, Las Palmas made it three wins from four games to move out of the relegation zone, with a 3-1 win away to Rayo Vallecano.
A header from Fabio Silva in the first half, followed by Aridane's 62nd-minute own goal and Manu Fuster's goal five minutes later gave Las Palmas another vital win under new coach Diego Martinez.