The 43-year-old's position as head coach of the Catalan outfit continues to be called into question, and there were rumours that he had started to lose the dressing room following the 4-1 defeat to Real Madrid in the Spanish Super Cup final last weekend.

Alarm bells would have been ringing when Varo Gomez sent third-tier side Unionistas ahead in the 31st minute of Thursday's last-16 affair.

However, Ferran Torres levelled the scores in the latter stages of the first period before Jules Kounde and Alejandro Balde registered in the second half to secure a 3-1 success for Barcelona.

The Catalan outfit's reward for their victory is a clash with Athletic Bilbao in the quarter-finals, with the draw for the next stage made on Friday afternoon.

Barcelona coach Xavi reacts on January 14, 2024 © Reuters

There will again be pressure on Xavi heading into Sunday's La Liga clash with Real Betis, but the manager refused to play down the importance of the cup success.

"I leave with a very good feeling, that we have improved in the game. Even when we were losing the match I had the feeling that we dominated it. And the second half is very good. We took a step forward. We played well," he told reporters after the match.

"Congratulations to Unionistas, they didn't seem like a third division team. We had a very strong rival ahead of us. They work very well with their manager Dani [Ponz]. It's not easy to attack a deep block.

"We had to match the aggression, courage and soul. On specific occasions they got the better of us."

Barcelona coach Xavi before the match on October 4, 2023 © Reuters

However, Xavi admitted that his side 'made mistakes again' during the match and acknowledged the need for consistency in the second half of the campaign.

"We make mistakes again. Errors in concentration, lack of aggressiveness. In today's case it is a ball that we lost in midfield due to lack of aggressiveness," he told reporters.

"In matches like this, when the rival defends so deep, we have to shoot from outside the goal.

"Sometimes we play very well and sometimes we have to play much better. Sometimes I get disappointed, because we don't do what we have to do, what is expected. We know that we have to win and play well. This is Barca."

Barcelona are still seeking success in La Liga, the Champions League and the Copa del Rey this season, and the team have won four of their last five games in all competitions amid the recent criticism.