Local newspaper Sport called the result an "historic humiliation" adding: "A ridiculous Barca suffered its biggest defeat in Europe, ending a lamentable season without a trophy for the first time in 12 years."
Daily Mundo Deportivo described the defeat on its cover as "A shameful end to an era", also declaring that coach Quique Setien would be immediately sacked as coach and that president Josep Maria Bartomeu would call an election imminently.
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National newspaper AS used the same headline as Sport, adding: "The disaster against Barca opens up a crisis with far-reaching consequences at every level of the club."
Marca used the word "shame" on its cover, adding that Setien, who was hired in January to try and restore some style and flair to the team, had "one foot and a half out of the door."
Sport gave defender Nelson Semedo a rating of one out of 10 after he was tormented by Alphonso Davies in the build-up to the fifth goal scored by Joshua Kimmich. It gave Setien a rating of zero, adding: "He cannot spend one more day in Barca's dugout."
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AS also said Setien's days at the club were numbered, adding that former Tottenham Hotspur coach Mauricio Pochettino was waiting in the wings, despite previously saying he would never coach Barca due to his loyalty to former club Espanyol.
The new follows comments made after the match by Bartomeu, who said decisions needed to be taken and ammouncements would follow in the next week.
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That night in Barcelona: United and the 1999 Treble