Barcelona coach Hansi Flick felt Eric García's early red card was the turning point in Thursday's 2-1 defeat to Monaco and insisted his side are strong enough to progress in the new-look Champions League.

García was dismissed after just 10 minutes for a last-man challenge before goals from Maghnes Akliouche and George Ilenikhena, either side of Lamine Yamal's equaliser, earned the Ligue 1 side three points at the Stade Louis II stadium.

The loss was Barça's first defeat under Flick following an impressive start to the campaign which has so far yielded five successive wins in LaLiga.

"I think we defended with a lot of passion," the German coach said in a news conference after the game. "The goal from Lamine brought us back to 1-1. We had chances. At the end, we tried to stay in the game with a compact defence, close together, but you can also see that [Monaco] bring a lot of players in with huge speed. It was not easy to defend.

"After the red card, the game changed totally. The positive things are we tried to defend as a team and attack as a team. We have chances, but they deserve the 2-1 so we have to accept that.

"I am not worried. We have to analyse this, but as I say to the team now, 'Heads up,' because they were a little disappointed in the dressing room."

Barça host Young Boys in their next Champions League game on Oct. 1 and still have to play Bayern Munich, Borussia Dortmund, Benfica and Atalanta, among others, in the competition.

The new format will see the top eight teams in the league phase progress directly to the round-of-16, with the sides finishing between ninth and 24th entering a knockout round and 12 teams being eliminated.

Despite opening with a defeat to Monaco, Flick has no doubts that Barça will qualify for the next phase.

"No," he responded when asked if Thursday's loss was further proof that Barça have a problem with the Champions League having failed to reach the knockout rounds in two of the last three years.

"You see the situation today. After 10 minutes, the red card. It changed totally our idea, our match plan. We have to accept this. It happens.

"I think we are strong enough to play a good Champions League. We have seven matches and I think we will win many matches and at the end we reach our goals."

The game changed when García hauled down Takumi Minamino after the former Liverpool forward intercepted a short pass from Barça goalkeeper Marc-André ter Stegen in the early stages of the match. Ter Stegen said the mistake was a misunderstanding between the two and claimed Barça deserved a point.

"Yes, for sure [the red card conditioned the game]," he told reporters. "There was a misunderstanding in that situation. I feel bad for Eric because it has cost him. Then we have to play for 80 minutes a player down.

"It should not have happened, but it does happen from time to time in football. It hurts because even with 10 men we showed up.

"The game was not under control, but we showed up. At the end of the day, we lost by one goal, the second one, which came from nowhere and wasn't really deserved in that moment."

Among the positives in defeat for Barça was the return of Ansu Fati, who returned from injury to make his first appearance of the season.

"I saw him in the last weeks of training and when we start the preseason, I saw him really different," Flick said.

"I spent some time at Brighton last season and I saw him in training and a match and here he is totally different. He's focused, he brings his quality on the pitch. He needs some time now, but he will get this."

Fati remains the youngest scorer in the Champions League at 17 years and 40 days old when he netted against Inter Milan in 2019, but he watched from the bench as teammate Yamal became the second youngest to score in the competition at 17 years and 68 days old.

Yamal now has four goals and four assists in six games in all competitions this season, which has seen opposing teams start to double up on him or treat him differently. As a result, Flick removed him early in Monaco to save him for Sunday's trip to Villarreal in LaLiga.

"Lamine today he tried a lot," Flick explained. "It was a tough match for him, they [were] attacking him really hard. This is the way. He has to adapt to this. For Pau [Cubarsí] and him, [taking them off] was also to think about Sunday."