Barcelona fielded a much-changed XI for their Copa del Rey trip to Levante, whose head coach Paco Lopez was nonetheless delighted with a surprise 2-1 win.
There was no Lionel Messi or Luis Suarez in the squad for the holders, who have lifted the trophy in each of the past four seasons, while Gerard Pique was also missing.
Levante raced into a two-goal lead inside 20 minutes through Erick Cabaco and Real Madrid loanee Borja Mayoral, only to see Barca grab a potentially crucial away goal through Philippe Coutinho's late penalty.
Ernesto Valverde's men will be widely expected to overturn the deficit at Camp Nou next week and reach the quarter-finals, but Lopez savoured a rare victory over the league leaders.
"Messi was not there, Suarez, [Gerard] Pique ... but if we go over the players that were on the field: [Ousmane] Dembele, Coutinho, [Sergio] Busquets ... for a team like ours to beat Barca has much merit," Lopez said.
"They were not the best players in the world, but I am very proud of having defeated Barca."
Asked if he felt the victory has forced Valverde to field a stronger XI in the return leg, Lopez replied: "I do not know, it does not depend on me.
"We wanted to win the match because in a tie it is very difficult to eliminate them. We will compete next week in the same way and think the same. I congratulate the team for the work and the effort.
"[The late penalty] is a shame, because although they had chances, the team has deserved to make it 3-0, but again, I'm very happy, we'll talk about the coming week of the return."