The Reds endured a sobering return to action as City, the side whose Premier League crown they took last week, served a ruthless reminder of their enduring quality at the Etihad Stadium on Thursday.
The outstanding Kevin De Bruyne began the rout from the penalty spot before further goals from the equally impressive Raheem Sterling and Phil Foden before half-time. An own goal from Alex Oxlade-Chamberlain completed the scoring.
"I'm delighted. Congratulations to the team, we beat the champions with the quality they have," he said.
"They didn't come here to celebrate. They'd drunk enough beers and they came here to compete.
"So the chances we created, to beat them 4-0, it was so important for preparing against Arsenal and Real Madrid."