Leicester punished wasteful Liverpool to clinch a 2-0 win and dump the Reds out of the Carabao Cup.
Shinji Okazaki and Islam Slimani struck in the second half after Jurgen Klopp's side failed capitalise on their first-half dominance.
Dominic Solanke, Philippe Coutinho and Alex Oxlade-Chamberlain missed decent chances before Liverpool wilted after the break.
They allowed Leicester to recover from what could have been a chastening first period and substitute Okazaki's introduction - coupled with Coutinho's withdrawal at half time - swung the game in the Foxes' favour.
It was first blood to the Foxes with Liverpool returning to the King Power Stadium in the Premier League on Saturday.
The Reds made eight changes for the third round tie to hand Oxlade-Chamberlain and Solanke full debuts with Leicester making seven, giving bows to Vicente Iborra and Aleksandar Dragovic.
But the switches initially refused to upset any of the visitors' rhythm as they bossed the first half without finding a crucial, and deserved, goal.
Ben Chilwell needed to produce an early excellent goal-saving block to deny Oxlade-Chamberlain after Liverpool opened Leicester up when Leonardo Ulloa was robbed by Marko Grujic.
Four minutes later Coutinho forced Ben Hamer into a smart stop when he skipped past three challenges with worrying ease.
Coutinho was the driving force and Hamer claimed his low effort as the hosts struggled to retain possession, constantly gifting the Reds the ball.
And they almost paid the price when Solanke stretched to plant Andrew Robertson's delicious cross over from six yards.
Apart from a tame Demarai Gray strike the Foxes were disjointed and sloppy with Slimani and Ulloa redundant as an attacking force.
Craig Shakespeare's side seemed outnumbered given the tempo of Liverpool's pressing but kept their defensive shape well enough.
The relentless Reds pinned Leicester inside their own half and more bright Liverpool work saw Robertson's drive fly across goal before Oxlade-Chamberlain shot at Hamer with half an hour gone.
Coutinho planted a free kick over and Solanke then wasted Liverpool's best opening seconds before half time when he lobbed over from close range following Coutinho's excellent pass.
The Brazilian was withdrawn at the break for 17-year-old Ben Woodburn and with the midfielder went Liverpool's zip.
They lacked the intensity of the first half and, with Leicester becoming more combative, the hosts finally grew into the game.
Gray dragged wide before the Foxes took a 65th minute lead through Okazaki, who had only been on the pitch 12 minutes after replacing the injured Ulloa.
Liverpool half cleared a corner and when it was hooked back in, Wes Morgan's header found Iborra and he nodded down for Okazaki to find the bottom corner from 15 yards.
There was little response from the Reds, aside from Oxlade-Chamberlain miscuing from 18 yards, and Leicester wrapped up the game with 12 minutes left.
Slimani had been virtually anonymous for most of the night but suddenly produced a rocket from the edge of the box, finding the top corner after Liverpool opened up.
Gray almost added a third, only for Danny Ward to turn his strike wide, but there was no way back for Liverpool who will seek revenge on Saturday.