Jules Koundé said Barcelona's players must take responsibility for the team's poor form after scoring the second goal in Thursday's 3-1 comeback win against third-tier Unionistas de Salamanca in the Copa del Rey.

Koundé rifled in from distance after Ferran Torres had cancelled out Alvaro Gómez's first-half opener, with Alejandro Balde sealing the Catalan side's passage to the quarterfinal in the 73rd minute.

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The victory slightly eases the pressure on coach Xavi Hernández, who ESPN reported is fighting to keep the players onside with a section of the first-team squad losing faith in him even before Sunday's defeat to Real Madrid in the Spanish Supercopa final.

"At the end of the day, you can talk about the coach, but we [the players] are the ones out there on the pitch," Koundé told Movistar after the win at Unionistas.

"When there are bad results, it's also our fault, of course. We had to react tonight. This game was important and we have to move forward with intensity, which is what I think we have lacked this season."

Despite last weekend's loss to Real Madrid and the fact they are eight points adrift of LaLiga leaders Girona, Barça still have plenty to play for this season.

They face Napoli in the round of 16 of the Champions League next month and Koundé is also targeting success in the Copa del Rey ahead of Friday's quarterfinal draw.

"Winning the Copa is one of the objectives and after a tough defeat on Sunday we needed to show a reaction," the France international added. "We put in a serious performance.

"It was difficult. [Unionistas] knocked out Villarreal in the last round and play good football if you give them time. I don't think we were bad in the first half, but the reaction [to conceding] was good."

Jules Kounde celebrates after scoring a goal for Barcelona in the Copa del Rey. Getty Images

A shock looked on the cards when Gómez opened the scoring for the third-division side in the 31st minute with a brilliant finish in front of a 6,246 sell-out crowd at the Reina Sofia Stadium.

However, Torres drew Barça level on the stroke of half-time before brilliant goals from Koundé and Balde clinched the win, with Xavi especially happy for Balde.

"I am delighted for him," the Barça coach said in a news conference. "He's a 20-year-old kid who had dipped because he received the criticism, but it happens. He has to rebel against that.

"He is unstoppable at times and he has so much quality, he just has to exploit it. If you stop him going outside, he can go inside. He is not always a 10/10, but you're not always excellent, this is football, this is life."

Xavi added that the win will "boost confidence" as Barça prepare to return to LaLiga action with a trip to Real Betis on Sunday.