With the game locked at 2-2 after 90 minutes, goals from the sibling duo of Iñaki and Nico Williams gave Bilbao the win in the additional period.
Iñaki Williams completed a remarkable turnaround, having only returned from the Ivory Coast the day of the fixture. He was part of the Ghana squad that was knocked out of the Africa Cup of Nations after a draw with Mozambique on Monday and flew back to Spain on Wednesday morning to link up with his Bilbao teammates for the cup tie.
It was another damaging loss for Barça, which lost the Spanish Super Cup earlier this month to archrival Real Madrid and finds itself eight points adrift of first place in La Liga, though the Blaugrana do have a UEFA Champions League matchup against Napoli to look forward to in February.
“The feeling I have is one of disappointment because a trophy has gone, and in that way too, losing in extra time,” Barcelona manager Xavi said after the game. “On the other hand, I feel proud of the young players as they were fantastic.
“The venue was very difficult as Athletic are an intense and aggressive team, the most physical in the league.”
The game got off to the worst possible start for Barça, failing to clear the ball inside the box after pressure from the hosts and falling behind after only 35 seconds when Gorka Guruzeta volleyed home after a rebound.
A slice of fortune allowed the Blaugrana to level things up in the 25th minute. Yuri Berchiche’s clearance was charged down by Robert Lewandowski, with the ball ricocheting off the Polish striker and finding the back of the net.
There was nothing lucky about the visitors’ second goal, however. Teenage rising star Lamine Yamal picked the ball up on the right wing and made his way to the edge of the penalty area before firing in a sweet left-footed strike.
The 16-year-old set a Copa del Rey record in the process, becoming the youngest player this century to score in the competition.
Oihan Sancet equalized for Bilbao after halftime, heading home a Nico Williams cross.
The two sides exchanged chances for the rest of regulation time, but neither team was able to edge ahead, leading to extra time.
Athletic came up with a huge goal just before the end of the first half of extra time – Iñaki Williams latched on to a through ball and fired a shot against the post, but fortune shone on him on this occasion as the ball rebounded directly into the forward’s path for a tap-in.
His younger brother Nico put the game to bed right before the full-time whistle, scoring with the outside of his right boot to seal the win for the Lehoiak.
An upset for the La Liga leaders
This season’s surprise package in Spanish football has been Girona, which is mounting the unlikeliest of title challenges in only the club’s fourth season of La Liga football.
However, the Blanquivermells will not get the chance to do the league and cup double after losing 3-2 to Mallorca on Wednesday.
Mallorca, which sits 14 places and over 30 points behind Girona in La Liga, raced into a 3-0 lead at home inside the first half to stun the league leaders.
Girona was offered a route back into the game when Mallorca captain Antonio Raíllo was sent off and Cristhian Stuani converted a penalty to pull a goal back, but the 10-man host stood firm.
Brazilian forward Sávio scored in the sixth minute of injury time to make it 3-2, but it was too little, too late for the visitor, which now has the league as its sole focus.
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