The defending LaLiga champions start their European journey at VfB Stuttgart tonight on the back of a 100% opening to their domestic campaign.
Flick has won back-to-back Spanish crowns across two years in Catalonia, but he's come up short in Europe, with semi-final and quarter-final exits in 2025 and 2026 respectively.
Former Barca boss Luis Enrique has gone on to win the UCL in both of those years and Flick admitted something has to give in the months ahead.
"All the big clubs dream of winning it. We have the quality to win it, but we have to prove it and the road is long.
"We have many experienced players in the squad. They all have the responsibility to try and win everything. It's not all easy after winning four games.
"There are players who aren't happy about not playing, but every day they have to prove that it's their time. Our level is what we've shown in training."