Javier Hernandez settled a cracking Capital One Cup tie with a winner at the start of the second half as everybody at Old Trafford showed how the champions respond to adversity.
The first half was a lively, evenly-contested affair with the hosts unable to really trouble Simon Mignolet as most of the shots on goal were deflected by the eager Merseysiders. Indeed, Brendan Rodgers' side carved out the clearer opportunities in the opening 45 minutes.
Daniel Sturridge fired a couple of attempts wide and David De Gea was out bravely to deny Luis Suarez on his reappearance from a 10-game ban. However, United started the second half in inspired form and, after Nani immediately won a corner, Hernandez gave Jose Enrique the slip to expertly touch in skipper Wayne Rooney's set-piece.
Jordan Henderson spurned a real chance but most of the pressure was now coming from the Reds with Nani twice firing over and Shinji Kagawa spinning Lucas and skimming the bar with a thumping drive from outside the area. Back came Liverpool with Suarez brushing the side netting and hitting the bar with a free-kick, either side of a Victor Moses diving header bringing the very best out of De Gea.
Rooney twice extended Mignolet with fine efforts as the game continued to go from end to end and De Gea had to fish away a mis-hit cross by Henderson at his near post, before Kolo Toure could not capitalise after Suarez got away with a shove on Jonny Evans. The ground was a cauldron of noise at the death to celebrate revenge for the league defeat at Anfield.