Three goals in 19 minutes stunned a Pep Guardiola side who had only been defeated a handful of times this season to put the 'Reds' as the favourites going into the second installment on Tuesday night.
However, Jurgen Klopp has a dilemma that not many managers have experienced against City: what is the best set-up to maintain an advantage over the 'Sky Blues'?
A natural human instinct would be to sit back and defend, like what Liverpool did in the second half, but that would invite constant pressure from their opposition who have to score at least three goals.
Although the margin seems significant, City boast numerous players who are very dangerous on the attack, such as Kevin De Bruyne, Raheem Sterling and Gabriel Jesus, and one goal early on would swing momentum heavily in their favour.
Liverpool aren't known for being defensively solid too, though they did manage to keep a clean sheet in the first leg, so arguably their best tactic could be to play a similar performance to the one they produced at Anfield: blitz City early on to dent their hopes of securing progression.
The latter seems like a more sensible option for the 'Reds' given that captain Jordan Henderson is suspended and their other midfield stalwart Emre Can is sidelined with a back injury, meaning it will have to be a make-shift central partnership to protect the back four at the Etihad.
Both scenarios have different pros and con for Klopp and which ever way he chooses to set-up, it won't be a straightforward 90 minutes despite their comfortable aggregate lead.