David Villa scored in the 83rd minute Saturday to give Spain a 1-0 win over Paraguay and its first-ever spot in the World Cup semifinals.
The ball fell to Villa in the area after Pedro Rodriguez hit the post and Villa took one touch before curling a shot in off the far post.
The striker's tournament-high fifth goal sets up a semifinal against Germany in Durban on Wednesday.
Paraguay's defense mostly kept Spain's vaunted attack at bay, and neither team couldn convert a penalty kick.
Spain goalkeeper Iker Casillas saved a 59th-minute penalty by Oscar Cardozo and Paraguay captain Justo Villar matched him on a retaken shot by Xabi Alonso two minutes later.
Paraguay controlled the start Saturday and tested Iker Casillas within 50 seconds as the Spain goalkeeper got down to stop Jonathan Santana's low shot.
Paraguay didn't sit back on defense but pressured Spain high to disrupt its slick passing game. Paraguay blocked Spain's first chance in the seventh minute - from Xabi Alonso - before Sergio Ramos nearly headed in from a corner kick.
The South Americans swarmed around Spain's area to force turnovers and Cristian Veros headed high in the ninth before Claudio Morel's shot was off two minutes later.
European champion Spain has fielded an unchanged lineup for the third straight game as it attempts to win a World Cup quarterfinal match for the first time against Paraguay.
Coach Vicente del Bosque stuck with misfiring striker Fernando Torres up front alongside David Villa, who has scored four of Spain's five goals to be joint-leading scorer in South Africa.
Oscar Cardozo and Nelson Valdez lead Paraguay's attack as it also aims to reach the semifinals for the first time.
Barcelona trio Xavi Hernandez, Andres Iniesta and Sergio Busquets plus Xabi Alonso make up Spain's midfield for Saturday's match at Ellis Park.
While Spain stuck with the same lineup, Paraguay coach Gerardo Martino made six changes from the team that advanced on penalties against Japan, including dropping Manchester City striker Roque Santa Cruz.
Paraguay, playing in its first quarterfinal, hadn't conceded a goal since its opening 1-1 draw against Italy.
Spain has never lost to Paraguay in three previous meetings, winning once and drawing twice.
Paraguay: Justo Villar, Dario Veron, Claudio Morel, Oscar Cardozo, Edgar Barreto, Jonathan Santana, Paulo Da Silva, Victor Caceres, Christian Riveros, Nelson Valdez, Antolin Alcaraz.
Spain: Iker Casillas, Sergio Ramos, Joan Capdevila, Carles Puyol, Gerard Pique, Sergio Busquets, Xabi Alonso, Xavi Hernandez, Andres Iniesta, David Villa, Fernando Torres.