Barcelona have set up a quarter-final showdown with Atletico Madrid in the Copa del Rey after defeating Elche 4-0 on Thursday.
Coach Luis Enrique rested all 11 starters from Saturday's 3-1 victory over Atletico Madrid for the match in eastern Spain, with B-team starlets Adama Traore and debutant Gerard Gumbau being handed opportunities to impress in the senior fold.
The winners of the tie would face Atletico Madrid in the quarter-finals, but La Blaugrana were considered outright favourites to progress, given the 5-0 lead they took from the first leg at Camp Nou.
Barca flew off the blocks as they came a whisker away from adding to their aggregate advantage through Munir El Haddadi, who was released in behind by Rafinha but could only slam the chest of Manu Herrera from point-blank range.
The Catalans proceeded to dominate the first half, and they were rewarded for their troubles when Jeremy Mathieu hammered a free kick into the top-left corner of the 33-year-old's net, his first goal for the club.
They doubled the lead inside the last five minutes, Sergi Roberto smashing an unstoppable strike from the edge of the box with his weaker left foot, before it was three and out moments later from the penalty spot.
Edu Alcabar, already on a yellow card, clipped the heels of Munir in the area, leaving Pedro Rodriguez with the task of sending Herrera the wrong way.
The second half proved more of the same, with Elche chasing shadows for most part, barring the occasional break. Traore and his replacement Alen Halilovic shared the most notable efforts, the Croat striking the post from a right-hand snapshot.
Munir then should have done better from a header after he was picked out at the far post, but Adriano settled the result deep in added time, guiding Douglas' maiden assist home to book Barca's place in the last eight.
Elche 0-4 Barcelona (0-9 agg)
Mathieu 21, Sergi Roberto 40, Pedro 43, Adriano 90
Elche: Manu Herrera; Peral, Lomban, Pelegrin (Fajr 79), Albacar; Galvez (Roco 69), Pasalic (Adrian 63); Coro, Alvaro, Fragapane; Cristian Herrera
Barcelona: Ter Stegen; Montoya (Douglas 62), Bartra, Mathieu, Adriano; Sergi Roberto, Gumbau, Rafinha; Pedro, Munir, Adama (Halilovic 62)
Referee: Jaime Latre