Ernesto Valverde described Barcelona's victory over Sevilla at Camp Nou as "crucial" and will act as a launchpad to sustain their title defence.
A sublime Luis Suarez overhead kick opened the scoring before Arturo Vidal and Ousmane Dembele gave Barca a 3-0 lead before the break.
Lionel Messi scored with a trademark free kick on 78 minutes but the match ended in chaos with Ronald Araujo, making his debut, and Dembele both shown red cards for the home side.
The win saw Barca move up to second in the table two points behind leaders Real Madrid, who visit Camp Nou for the first Clasico of the season in three weeks' time following the international break. Atletico Madrid are third on 15 points after drawing 0-0 at Real Valladolid.
"It was crucial for us," Valverde said of the victory. "It has been a strange start to the season and we have not added all the points we would have wanted."
Barca rode their luck in the opening exchanges as Sevilla looked menacing and inventive going forward but lacked the killer touch.
Julen Lopetegui's side were made to pay for their profligacy as Barca effectively sealed the match in an eight-minute scoring spree.
Suarez gave the champions the lead with an outstanding bicycle kick in the 27th minute and Chile midfielder Vidal connected with an Arthur Melo shot-cum-cross to steer past Tomas Vaclik on 32 minutes.
Frenchman Dembele, who started ahead of €120 million (Dh484m) signing Antoine Griezmann, made it 3-0 in the 35th with a superb solo dribble and finish.
Captain Messi, whose early season has been hampered by a calf injury, curled over a superb free kick on 78 minutes, the Argentine's first of the campaign.
Uruguayan defender Araujo, on for the injured Jean-Clair Todibo but was sent off 14 minutes later for a last-ditch challenge on Javier Hernandez, while Dembele was dismissed for protesting the decision.
Referee Antonio Mateu Lahoz explained in his report that he showed Dembele a straight red card for saying "very bad, you are very bad" and waving his arms at him.
"Dembele's [red card] is a mystery," said Valverde. "It is very difficult to get words out of him in Spanish, so what he said couldn't have been very long."
The forward will automatically miss Barca's next La Liga fixture at Eibar and could see his ban extended to two games, ruling him out of el clasico, if La Liga follow recent precedent of others who have lashed out against referees.
be suspended from Barca's next La Liga game at Eibar and is in danger of missing the 'Clasico' against Real, as players who have said similar words to referees in recent seasons have been handed two-game bans.
Barca's scorer Vidal said they deserved the big victory.
"We were superior to them the whole time, we were always putting them under pressure and we are worthy winners," he told reporters.
"We were up against a team who are good with the ball and on the wings but we dominated them in those areas."
Lopetegui's last visit to the Camp Nou was a painful affair as his then Real Madrid side were hammered 5-1 by Barca in his final game in charge before being sacked, and this was a similarly galling experience for the former Spain coach.
"It's a crushing and undeserved defeat," he said Lopetegui. "We played very well, we were brave and we tried to do what we had worked on in training but we couldn't take our chances."
