In the Copa del Rey semi-final first leg, Barcelona faced an early setback as they conceded two quick goals within the first six minutes. Despite a valiant effort to fight back, they ultimately let in two more late goals, one of which came from Sorloth in stoppage time, resulting in a thrilling 4-4 draw.
"I think we have had really two great matches and of course we have to be focussed from the beginning to the end of the match," Flick told reporters Saturday.
"I think in the first match, at the end of the match we were not so focussed like we can be, and also the second match was (the same) in the beginning and also at the end, so we have to take care about that.
"When you make mistakes Atletico can hurt you and this is what we have to defend against."
Atletico Madrid were knocked out of the Champions League on Wednesday on penalties by rivals Real Madrid, while Barcelona beat Benfica to reach the quarter-finals.
Former Manchester City striker Julian Alvarez scored a penalty in the shoot-out for Atletico which was controversially disallowed because he may have touched the ball twice when he slipped as he took it.
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"It was an unlucky situation, I feel for him, he's one of the best strikers," said Flick, adding that it was "not a problem" for Atletico to have played 120 minutes because of their squad depth.
Atletico coach Simeone was still upset about the decision to rule out Alvarez's penalty.
"Normally I would (say I'm only speaking about) Barcelona, but this time the situation deserves for me to explain my feeling of anger, but it is in my hands to continue working so that the team continues to compete," Simeone told reporters.
'Rage and injustice'
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"The feeling we all have is one of anger, rage and injustice."
Flick has plenty of options himself with Dani Olmo seemingly ahead of Gavi in the pecking order for the attacking midfield spot.
Gavi and Barca defender Alejandro Balde were not included in the Spain squad to face the Netherlands in the Nations League quarter-finals next week, but the Barca coach hailed both players.
"(Gavi) came from a huge injury and he's 20 years old and now at the moment he is I think, not the first (choice)... a more difficult situation but he's doing great," said Flick.
"At the moment our midfield is doing really good. I'm happy he's here and I think he will play many, many years for this amazing club and be one of the superstars here.
"He can improve a lot, he will do this. His attitude is unbelievably good, he's really focussed and really happy he is here.
"I think for the World Cup 2026 he will be there and be able to play, 100 percent."
Flick said Balde was "one of the best" left-backs in the world, and also praised veteran centre-back Inigo Martinez, who was called up for Spain by national team coach Luis de la Fuente.
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"With his attitude and mentality he's unbelievably good for every team," added Flick.
(This story has not been edited by staff and is auto-generated from a syndicated feed.)