After being pegged back twice, Barca were able to pull away in the second-half as they reached the quarterfinals 8-3 on aggregate.
Flick said afterwards: “The first half was very tough. We knew they would press but they were very good man to man. After we scored the first everything went up and down. I was very happy when we scored the third goal.
“The solution was always to play progressively but we lost the ball many times and because Newcastle are very fast it wasn’t easy to defend. I asked the players at half-time to have more precision, to push Newcastle deep and it worked well.
“We will analyse this, we want to improve and we will, but the last line of our defence is doing a really great job. The pressing on the ball today was very good and we didn’t make it easy for Newcastle to play out.”
Flick added, “I liked that we said specific things at half-time and the players did it. As a coach it’s always good when the players listen and then produce. I saw new, improved confidence in that second-half performance. Mine is a very young team but they always try to be better and they keep improving.
“The next round also looks like it will be very difficult. We have to go step by step, match by match; that’s what we did last season and will do again.”