Speaking after the final training session, the Barcelona coach stressed focus and defensive discipline, with his side chasing a top-eight finish in the competition.
"We deserved to win, but that's football," Flick said. "Now, on Wednesday, it's time to win in Prague. We have to be one hundred percent defensively or we won't be able to win the game."
Barcelona travelled without two key attacking players. Lamine Yamal was ruled out through suspension after accumulating yellow cards, while Ferran Torres was sidelined with a hamstring injury. The club confirmed that Torres had suffered a problem with the semimembranosus muscle in his right leg, with an expected recovery time of around ten days.
The injury means Ferran missed Champions League fixtures against Slavia Prague and Copenhagen, as well as the La Liga match against Real Oviedo. If his recovery goes to plan, he could return away to Elche on January 31 and should be available for the Copa del Rey quarter-final against Albacete.
Ferran's absence was a significant blow. He had been Barcelona's leading goalscorer across all competitions this season and Flick's preferred striker ahead of Robert Lewandowski. The Spain international picked up the injury during the match against Real Sociedad before being substituted.
In response, Flick was expected to turn back to Lewandowski through the middle. Marcus Rashford was another option, having played centrally before, while Dani Olmo could also be used as a false nine with Fermín arriving from midfield.
There was positive news in the squad. Raphinha returned after receiving medical clearance, having missed the previous match with a knock. Flick welcomed his availability, saying the team must "always give their best at this level," with full focus on the next challenge.
Vincent Kompany has doubled down on his belief in attacking freedom, with Bayern Munich's remarkable goalscoring record this season offering strong evidence that his approach is working.
Pep Guardiola has brushed aside Manchester City's derby defeat to Manchester United and immediately turned his attention to the Champions League tonight.
Alvaro Arbeloa has moved quickly to defend Vinicius Junior after the Brazilian winger was booed by sections of the Santiago Bernabeu during Real Madrid's 2-0 win over Levante, insisting the forward remains one of the best players in world football.
Thomas Frank has insisted he still felt the backing of the Tottenham Hotspur board as he prepared his injury-hit squad for a crucial UEFA Champions League clash against Borussia Dortmund tonight.
