Barca won 5-4 on Tuesday night, with Raphinha and Robert Lewandowski both scoring twice.
Afterwards, Flick praised his players' attitude on the night.
The match:
"It was a crazy game. The most positive thing is the mentality. We came back and it's wonderful. It's football and that's why we love it. I think Benfica did well. We didn't defend well. We wanted to achieve something different in the second half, to get back into the game... the team's mentality was incredible. They always believed. I was very happy. It's a fantastic result."
Have you ever experienced a comeback like this?
"I don't think so. We didn't play so well in the first half. They were very good in transitions. They made us defend very deep. We weren't in the right position. In the second half, we were better. The changes helped us a lot in the comeback. We talked about Szczesny before the game and he made several mistakes, but he made a good save at the end."
Szczseny?
"What player doesn't make mistakes? It's normal, we win together and we lose together. It's not just about one player. The mentality... sometimes you have to play like that. I liked what I saw in the second half. I think we have to analyse everything now. He and Iñaki played very well. The decision was for the team, we'll see what happens on Sunday."
Into the playoffs:
"It's very important for us to focus on Valencia first and then we want to beat Atalanta. We can't think we're comfortable, not at all."
Performance:
"All players make mistakes, not just Szczesny. He saved us too. We're back and now we have good memories of Lisbon. It was an incredible game, with a great performance. We created chances, especially in the second half. We believed."
Benfica:
"I'm not surprised. They're one of the best teams in transition, and the coach has done a great job. But I didn't see the penalty play, I trust the VAR and it has decided. Sometimes it goes in favour and other times it goes against."
Defensive errors:
"We have to analyse the games. We will train and discuss it in the talks. We will teach the players what they have to do better."
Pedri:
"In the first half, he made a few mistakes, but he wanted the ball. He creates. He creates space for players to pass... for us, he is very, very important. At 4-4, he made the final pass. He always creates opportunities to win. He has a great mentality, it's beautiful to watch."