By SABC Sport
9th January 2025
Gavi opened the scoring after just 17 minutes at King Abdullah Sports City in Saudi Arabia, ahead of a 52nd minute Lamine Yamal strike.
The result ended Athletic's cup campaign as Barca secured a final with one of Real Madrid or Real Mallorca, who play their semi-final on Thursday.
Williams was frustrated after seeing his 86th-minute strike ruled out following a Video Assistant Referee check.
Speaking after the game, the Ghana internationl was reported by Ghanasoccernet to have said: "It was like playing away from home. I find it strange that these types of plays are cancelled.
"I don't think it's fair. It seems that the rules are not the same for everyone."
Athletic are next in action at home to Osasuna in the Copa del Rey last 16 on Thursday.