Atletico Madrid slumped to a stunning 3-0 loss at Osasuna on Sunday, leaving Real Madrid as the sole leader of La Liga for the first time since May 2012.
Osasuna beat Atletico at their own game, both in their tough, physical approach and their set piece strategy to take a three-goal lead at the break after one of Atletico's worst first halves in three years under coach Diego Simeone.
Alvaro Cejudo opened the scoring from a corner kick in the sixth minute before fellow forwards Emiliano Armenteros and Roberto Torres added goals in the 21st and 42nd.
Osasuna used a bit of well-executed trickery to strike first when they sent several players to the near post to draw in Atletico's defense before Torres crossed to the far post, where Cejudo had charged in late to drive the ball home.
Osasuna were a step faster to almost every ball and Armenteros beat Gabi Fernandez to a loose ball before he unleashed a blistering left-footed strike from outside the area that went in off the post.
Diego Costa mustered a shot that sailed wide in the 21st, but Atletico never responded to Osasuna's surge and a collective breakdown in defense cost them a third goal. David Villa first failed to fight for a ball in midfield, and then two defenders left Torres unmarked to nod Damia Abella's cross under goalkeeper Thibaut Courtois.
Atletico's loss came one day after Barcelona lost 3-1 at Real Sociedad, with both the former front-runners looking weary after their Champions League trips in midweek.
Real Madrid lead their two title rivals by three points, the first time they have topped the standings since winning the title in 2011-12.
Earlier Sunday, Athletic Bilbao strengthened their hold on fourth place by winning 2-0 at Real Betis after the bottom side had two players dismissed.
Seconds after Betis' Ruben Castro was booked for diving in the area, Bilbao forward Iker Muniain scored from a spot kick in the 34th minute after Damien Perquis tripped Kike Sola from behind on the edge of the area.
Another reckless tackle by Perquis earned him a second yellow card in the 41st minute. Betis was left with nine men from the 58th minute when Lorenzo Reyes handled the ball after he had already been booked for arguing.
Bilbao squandered several scoring chances until substitute Guillermo Fernandez headed in the first ball he touched in the 81st minute.
Bilbao's first victory in four rounds lifted them four points clear of Real Sociedad and kept them in command of Spain's last Champions League berth for next season.
Valencia and Sevilla both won to move to within five points of sixth place and Spain's last Europa League spot.
Valencia needed an injury-time goal from 19-year-old defender Ruben Vezo in his first start to complete a 2-1 comeback win at home over a feisty Granada.
Piti put Granada ahead in the 47th, but as the visitors' tired Valencia substitute Paco Alcacer tapped in Sofiane Feghouli's pass to level in the 64th. Valencia kept pressing and Vezo volleyed in a free kick headed on by a defender to claim the hard-fought win.
Sevilla won 1-0 at Rayo Vallecano to end a six-game winless streak.
After a drab first half by both sides, Coke headed home Ivan Rakitic's free kick to grab the 57th-minute winner at Vallecas Stadium.
Unai Emery's team played the last seven minutes with 10 men after Vicente Iborra received his second booking for taking too long to leave the pitch after receiving medical assistance.
Information from The Associated Press was used in this report.