Jurgen Klopp says Liverpool earned an important lesson against RB Salzburg on Wednesday.
The Reds were cruising in the first-half after Sadio Mane made it 3-0.
But a defensive capitulation meant the scores were tied with 30 minutes remaining, only for Mohamed Salah to save the day with the winning goal.
Klopp said: "The first 30 minutes was some of the best football we played so far, I would say, against a very good organised team with a clear identity. We did everything that they don't like on high speed, scored the three goals, could have scored more.
"They changed the system - that's allowed and not really a problem usually but tonight it was for us. We changed, for some reason, the approach. Some were in a controlling mood, some were in an attacking mood, and other positions were too hectic.
"The other problem was that we tried to finish our situations off through the middle of the park. They had one midfielder less in the defence because they took a little bit more risk, left a No.10 between the lines, and we still tried to push through the centre.
"[We] lost the balls there, they passed the ball to the 10 and he could turn at the back of Fabinho: counter-attack. That changed the momentum of the game."
