With rivals Real Madrid struggling to fit new signing Kylian Mbappe into their stellar squad, and winning only one game so far, Barça have opened up a lead at the top of the league standings on nine points, two ahead of second-placed Villarreal and three from Celta Vigo in third.
A revamped Atletico Madrid and Real are fourth and fifth on five points.
"It's going to be a long season and I'm not focused on the opponents. I'm focused on Barça, we've done well in the first three games and hopefully tomorrow we'll be victorious," Flick told a press conference on Friday ahead of Saturday's home game against Real Valladolid.
"The players are fit and rested, they are training really well and I'm pleased. We believe in our strength and in our idea of the game.
"Of course, there are many things we need to improve, like being focused from the start of the matches and not wait 10 minutes to get going.
"To be confident from minute one, that's what I expect from the players. It sounds like something basic but it's part of the hard core of our idea of the game. The quality of this team is sky high, fantastic."
Barcelona had to fight back to win after conceding first-half goals at Valencia and at Rayo Vallecano and needed a late Robert Lewandowski winner to break the deadlock at home against Athletic Bilbao.
Flick said he was delighted with the strength of character in the team.
"We have a special atmosphere and a very good mentality. They are very professional players with a great attitude. They are acting as one. The attitude, the mentality, the teamwork... I love it. This is the only way to win, in unison," Flick said.
