Sheffield United 3 Aston Villa 1
Villa, who have now been dumped out of the FA Cup at the third round stage for the last four years, were over-run by the play-off chasing Blades.
Midfielder Michael Tonge gave an early warning, firing over the top from the edge of the area before Liddell picked out Phil Jagielka and the blonde-haired midfielder's fierce low 15-yard strike flashed wide of the far post.
Keeper Paddy Kenny's poor throw out let in Gareth Barry whose powerful cross was too high for Carlton Cole as he surged into the box before Thomas Sorensen produced the first of a string of saves top keep Villa in the game.
The Danish international was quickly down to keep out Alan Quinn's low strike in the 17th minute before tipping over Jagielka's looping header after neat work by Liddell.
Andy Gray found a gap after a neat back-heel from Liddell in the 29th minute but his fierce 15-yard strike was snapped up by Sorensen.
Full-back Mark Delaney caught United on the break as he picked out Cole whose volley was too close to keeper Paddy Kenny before Sorensen produced a stunning save in the 33rd minute to foil Jagielka.
Against the run of play Villa snatched the lead in the 47th minute. Lee Hendrie threaded the ball to Barry who nipped between Leigh Bromby and Danny Cullip to beat Kenny with a right-foot shot from just outside the area.
United were level eight minutes later after winning a corner on the right. Liddell touched the ball to Jon Harley, his left-foot cross was missed by Delaney and Jlloyd Samuel as Cullip nipped in to stab the ball home from close range.
Liddell fired a free-kick straight at Sorensen after Harley had been upended before Tonge weaved his way in from the left before firing across the face of the goal.
Villa were more composed after the interval and when Barry picked out Hendrie in the 80th minute, his first-time shot flashed wide of the target.
However, two late goals sank Villa. Substitute Nick Montgomery's long ball down the right was flicked on by Quinn and Liddell, who looked two yards offside, stabbed the ball through Sorensen's legs from 12 yards.
He killed off Villa 60 seconds later when he ran onto Tonge's pass and hit the ball home first time from the edge of the box.
MAN OF THE MATCH: Andy Liddell (Sheffield United) - Capped an outstanding overall display with a late brace that finally killed off Villa.