Not only did Borussia Dortmund deliver a scintillating attacking display at the Eithad stadium, they also provided the world with a lesson on how to defend.
Jurgen Klopp's men were perfectly drilled in their defensive duties, responding to certain things whilst ignoring others.
Whether Manchester City had the ball on the half-way line or in their own half, Die Schwarzgelben would drop into a 4-4-1-1, cede possession and wait patiently.
When City ventured forward, the reigning Bundesliga champions would swarm the man with the ball quickly and exercise pressure using two or three players.
Even the unflappable David Silva suffered due to this, sparking further questions as to why City's men can't replicate league form in Europe.