Barcelona coach Hansi Flick remains unconcerned about his team's performance despite their 2-1 defeat to Monaco in Thursday’s Champions League opener.

Monaco capitalized on an early advantage after Barcelona's Eric Garcia was sent off just 11 minutes into the match, with goals from Maghnes Akliouche and George Ilenikhena sealing the victory for the French side.

Flick, who has led Barcelona to a five-match winning streak in La Liga, remained positive after his first defeat in charge and urged his players to focus on the upcoming games.

"With (Garcia's) red card, the game changed totally, but I can see the positives. We tried to defend as a team and attack as a team. We had chances, but they deserved to win," Flick told reporters.

"I have told the team to lift their heads up because they are disappointed, but we have to focus on Sunday's La Liga match at Villarreal, which is our next game. It’s time to recover, and hopefully, players will be back with a lot of energy.

"We have players that gave more than 100%. Every player tried to give their best in this situation. I’m really proud of this team, but we have to accept how we lost today."

Barcelona relived bitter memories of last season when they crashed out of the Champions League quarterfinals, losing 4-1 to Paris Saint-Germain after defender Ronald Araujo was shown a red card.

Flick denied that the Catalans struggle in Europe’s top club competition and said he is optimistic about their chances in the tournament, which they last won in 2015.

"Today, you see this situation with a red card after 11 minutes – it changed our match plan, but we have to accept it. This happens," the former Bayern Munich manager said.

"But we are strong enough to play a good Champions League. We have seven matches ahead, and I think we will win many."

Barcelona will host Young Boys next in their second league-phase fixture.