Flick, whose Barca reign has started with four consecutive victories, enjoyed watching Girona last season as they took LaLiga by storm, going toe-to-toe with Real Madrid in the title race and reaching the Champions League for the first time.
But despite heaping praise on rival manager Michel's work with their unheralded neighbors, who finished third, Flick said there will be no sympathy when they step on the pitch.
"We've won four games in a row and we have to keep going," Flick told a press conference on Saturday.
"I know it will be complicated because Girona play really well, it's a match at the highest level, Champions League level, and we're playing away. But we are confident because we have quality.
"Last season I watched Girona a lot and I was really impressed by what the coach did and how the players responded.
"But we know how we have to play and I'm sure the players will deliver. We must not look back. What happened, happened. The key on Sunday is that all our players give their best out there."
Barca are top of the standings with 12 points, one ahead of Villarreal, who have played a game more, four in front of Real Madrid and Atletico Madrid and five above fifth-placed Girona, who are coming off solid wins against Osasuna and Sevilla.
Flick said his team needed to make Girona uncomfortable and dominate possession against an exciting attacking side who won 4-2 in both LaLiga games against Barca last term.
"We know that Girona's strength is having the ball. We have to press well, defend as a block, stay well positioned and not give them any space," Flick added.
"It will be a tactical battle but we want the ball and, if we have it, we have a good chance of winning. It will a good test for us, it will be like a Champions League match."
