Alhassane Bangoura and Leo Baptistao guided Rayo Vallecano to a 2-1 win over local rivals Atletico Madrid on Sunday night.
Atletico, who are up in second place on the league table, were not near their best on the night and only managed a late consolation goal through Radamel Falcao in the fifth minute of stoppage time.
Vallecano took advantage of Atletico's inability to defend crosses into the area from the start and just three minutes in they opened the scoring when Piti's cross was not dealt with and Bangoura tapped in from inside the six-yard area.
Thibaut Courtois then had to make a good save to deny Alejandro Dominguez's strike but the hosts would get their second just after the half-hour mark.
Baptistao beat Cata Diaz to the ball and turned it in at the near post as Atletico struggled to make an impact.
Simeone replaced Adrian Lopez with Arda Turan at the break and the visitors created their first decent chance of the second period when Falcao was picked out in the middle but his header failed to trouble the goalkeeper.
Martinez Ruben then had to make a good save to deny Filipe Luis while Turan went close with a strike that fizzed past the post.
Atletico would get a goal late on when Falcao finished from close range with the last kick of the game but it was too little too late.