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After opening its European campaign with a 2-1 away win over Newcastle United, Flick's side fell to a 2-1 defeat against reigning champion Paris Saint-Germain. 

Barca also suffered a shock 4-1 loss to Sevilla in LaLiga off the back of that defeat, but on Sunday, it emerged from the international break with a 2-1 win over neighbour Girona.

The 2024-2025 semi-finalist is 16th in the Champions League standings, with its midweek visitor, Olympiacos, in 29th and still winless after a draw with Pafos and a loss to Arsenal. 

"The victory against Girona was very important and it has been noticeable in the atmosphere of the training," Flick said. "We have a young team and we needed it. We have analysed the match and we must run more and press better.

"They [Olympiacos] are very good offensively and we have to be attentive to their attackers. They have a clear idea of their game and we will have to be alert."

This will be just the third meeting between Barca and Olympiacos, with the previous two coming in the 2017-2018 group stage in the Champions League. Barcelona won 3-1 in the home fixture, before drawing 0-0 in Greece.

Barca has scored at least one goal in each of its last 22 Champions League matches, netting 58 goals in that span.

If it finds the net on Wednesday, it will be its second-longest scoring run in the competition, only behind a 29-game streak between November 2009 and March 2012, recorded under Pep Guardiola and including a 2011 final win over Manchester United.

Flick, who has made the Blaugrana one of Europe's most entertaining sides since taking the reins last season, now feels a sense of belonging in Catalonia.

"Now I feel the emotions more, this club has changed me completely," the former Germany and Bayern Munich boss said.

"I love Barca, I love the city of Barcelona and the people here. I give my all and live for the club."