Atletico Madrid have slipped to 11 points behind La Liga leaders Barcelona following a 3-0 defeat at Athletic Bilbao.
After a goalless first half, the hosts took the lead in the 50th minute when Mikel San Jose headed in powerfully from a corner.
Madrid pushed hard for an equaliser, but they struggled to create many decent chances.
Diego Costa saw his header fly straight into the arms of Gorka Irzaioz, while the Bilbao goalkeeper pushed away Raul Garcia's shot soon after.
The home side secured themselves the victory in the 77th minute as Markel Susaeta fired the ball into the bottom corner before Oscar de Marcos added another with five minutes left following a quick counter-attack.
