Athletic Bilbao's Spanish midfielder #24 Benat Prados and Barcelona's Uruguayan defender #04 Ronald Araujo vie for a header next to Barcelona's Dutch midfielder #21 Frenkie de Jong during the Spanish Copa del Rey (King's Cup) quarter final football match between Athletic Club Bilbao and FC Barcelona at the San Mames stadium in Bilbao on Jan 24, 2024. (PHOTO / AFP)

Athletic Bilbao beat Barcelona 4-2 at home to knock them out of the Copa del Rey on Wednesday as brothers Inaki and Nico Williams struck in extra time in a breathtaking quarter-final.

The hosts grabbed an early lead with a Gorka Guruzeta strike from a rebound inside the first minute but Barca managed to hit back before the break with two goals within five minutes.

Athletic's Yuri Berchiche attempted to clear the ball from his own six-yard box but it cannoned off Robert Lewandowski and into the empty net in the 27th minute.

Lamine Yamal then produced a moment of magic as he burst past three defenders to the edge of the box where he cut inside and slotted a brilliant strike just inside the far post.

In extra time, Athletic turned their superiority into goals. First Inaki Williams fired home a rebound from his own close-range strike that came back off the post two minutes into added time before the break and Nico Williams secured the win in the last action of the game, with a fine curling strike into the top corner

Athletic, however, fought back after the break and levelled in the 49th minute with a towering header by Oihan Sancet from a splendid cross from the left by Nico Williams.

As Athletic pushed for a third, with the skilful Nico Williams creating all kinds of trouble for Barca's defence, they were often exposed on the counter and 16-year-old Yamal missed two easy chances from close range.

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In extra time, Athletic turned their superiority into goals. First Inaki Williams fired home a rebound from his own close-range strike that came back off the post two minutes into added time before the break and Nico Williams secured the win in the last action of the game, with a fine curling strike into the top corner.

"Not even in the best of dreams I have seen this coming," Inaki Williams, who just hours earlier had arrived from the Ivory Coast, where he played in the Africa Cup of Nations with Ghana, told TVE.

"Everything went perfectly today. Yesterday I couldn't imagine being here after a very hard blow (Ghana's elimination).

"I have to thank the club for helping me to be here as soon as possible and the fans for embracing me the way they did."

Barcelona's Lamine Yamal fights for the ball with Athletic Bilbao's Daniel Vivian and Inigo Lekue during the Copa del Rey quarterfinals soccer match between Athletic Bilbao and Barcelona at the San Mames stadium in Bilbao, Spain, on Jan 24, 2024. (PHOTO / AP)

Athletic join Real Sociedad, Mallorca and the winner of Thursday’s clash between Atletico Madrid and Sevilla in the semi-finals.

Real Sociedad won 2-1 at Celta Vigo on Tuesday while Mallorca knocked out surprise LaLiga leaders Girona 3-2 earlier on Wednesday.

The loss will not help to ease the pressure on Barcelona manager Xavi Hernandez in a stuttering season.

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Barca are third in the LaLiga standings on 44 points, eight behind leaders Girona and seven adrift of rivals Real Madrid in second.

"I am calm, the most important titles remain," Xavi told TVE, referring to LaLiga and the Champions League, where Barca will play Napoli in the last-16.

"We tried, I think we competed well against a great team who are very strong at home. I said at the draw that we were unlucky. We had the winning goal with Lamine's chances, but we can be proud that we tried."