Copa del Rey has Real Sociedad, Athletic Bilbao, Granada, and second-division club Mirandes as its four semi-finalists, after both Real Madrid and Barcelona failed to make it to the last four in a decade.
The new edition of the Copa del Rey claimed the largest number of casualties on Thursday, and Real Madrid and Barcelona were eliminated in the last eight.
Real Madrid lost 4-3 to Real Sociedad at home, before Barcelona scored a late goal to lose 1-0 against Athletic Bilbao on the most surprising night in a competition filled with surprises.
Valencia also lost the defending champions on Tuesday and Villarreal were excluded on Wednesday. Sevilla and Atletico Madrid had already been sent off in previous rounds.
The semifinals will only be played in two stages this season, giving smaller clubs more chances to beat larger teams.
The last four surprises will also include Granada and the second division club Mirandes. This is the first time in ten years that neither Madrid nor Barcelona have reached the last four cup games, as at least one of the Spanish powers reached the final each year since the 2009-10 season when Seville won the title. Barcelona reached the final in the past six years in a row.
"This is the new Copa," said Barcelona midfielder Sergio Busquets. "We are playing a game, away from home, and in one play you are eliminated."
Real Sociedad finished a series of unbeaten matches in Madrid 21 by beating Santiago Bernabeu to reach the semi-finals for the first time in six years.
Athletic beat Barcelona thanks to the winner of Inaki Williams three minutes after the end of the second half, adding to the difficulties faced by the club since coach Ernesto Valverde expelled him and replaced him with Kick Sitan.
Barcelona has not yet been affected by the new coach, and the players and managers of the club have disagreed recently.
"I think we have taken a step forward. We are playing better than our opponent," Setien said. "Everything went well, except for the result."
Barcelona dominated during the second half and was on the verge of breaking the deadlock with clear potentials for Antoine Griezmann and Lionel Messi. But it was Athletic who found the late winner when Williams threw a header in the far corner after the Ibai Gomez crossing.
Athletic, the second most successful club in the cup with 23 championships, behind Barcelona, needed a penalty shootout to advance against second division clubs in the previous two rounds.
Messi appeared in its seventy-fifth session in the Cup, in keeping with Joseph Samiter's record in Barcelona since 1932.
Real Sociedad's victory stopped a series of eight wins in Madrid and gave the club its first defeat in all competitions since October.
He also ended Madrid's hopes of winning the cup competition for the first time since 2014.
Real Sociedad, semi-finals in 2014, will seek to win the third Copa del Rey Cup, the first since 1987.
"Our fans deserve a prize like this," said Real Sociedad coach Imanol Alguacil. "This victory means a lot, it comes in full Bernabeu, against a team like Real Madrid, with our team playing well." You can imagine how we feel now. "
Visitors dominated most of the match, but Madrid was about to return after scoring goals in the second half.
"We did everything we had in the end, but it was too late," said Madrid defender Marcelo. "It is difficult to come back after receiving four goals at home. It is disappointing, but we still have other competitions."
Madrid was partly dominant thanks to their strong defense, having only received 13 goals in 22 Spanish league matches.
The young Norwegian playmaker Martin Odegaard, who played for Real Sociedad on loan from Madrid, did not celebrate after he opened the scoring in the 22nd minute of the match after being saved by Madrid goalkeeper Alphonse Areola.
Young Swedish striker Alexander Issac joined the lead two minutes into the second half, a shot in the 54th and a shot in the top corner in the 56th
Isaac, 20 years old, has scored in five consecutive games, already scored an offside goal after reviewing the video just a few minutes after the break.
Marcelo approached Madrid with a low shot from inside the area in 59th, but Mikel Merino again increased the advantage for visitors at close range in 69th.
Rodrygo scored second in Madrid in 81st, two minutes after Vinicius Jr.'s goal was canceled by the video review. The third came through ahead from Nacho Ramos three minutes after the time of detention.
Real Sociedad defender, Andoni Gorosabel, was sent off before the final whistle.