Ten-man Villa KO Blades

Former United full-back Kyle Walker had put Villa in front early on with a goal on his debut, while Marc Albrighton doubled the advantage before the interval.

Sheffield United were given a route back into the game when Jamie Ward converted a dubious penalty, and the pressure increased on the Premier League side when Ashley Young picked up a second yellow card in the final quarter of an hour.

But a Stiliyan Petrov strike deep into injury time settled the tie.

Aston Villa came into the game having slipped into the Premier League relegation zone with manager Houllier under pressure.

Accordingly he named a strong side, with Gabriel Agbonlahor brought in to lead the line in the absence of the suspended Emile Heskey and loan signing Walker handed his debut.

The Blades came into the game with problems of their own and a new manager, Micky Adams, still settling into the role. They began brightly enough, however, with plenty of possession and an early volleyed effort from Robert Kozluk.

But after nine minutes the Premier League side took the lead with a goal from Walker: he picked up the ball on halfway and his run forward was largely unchallenged before placing a left-foot shot low into the corner.

The goal failed to change the pace of the game greatly. The Blades continued to apply pressure, going closest when Ched Evans forced a sharp save from Brad Friedel after a route one move.

But it was Villa who scored next with a flowing counter-attack led by Young. Dancing down the left, he picked out the onrushing Albrighton with a short cross - and the youngster obliged with a confident volley to score.

Houllier looked far from happy on the touchline, perhaps concerned more with Villa's lacklustre first-half showing than the scoreline.

And after the interval they were dragged back into the contest after the Blades were awarded a penalty. It looked as if Carlos Cuellar had made plenty of contact with the ball, but Lee Williamson fell to the ground and Ward slammed the penalty low into the middle of the net.

United applied plenty of pressure, but the second goal would not materialise. Friedel was called into action to deny a long-range effort from Daniel Bogdanovic, and Nick Montgomery hit a volley which did not make its way through the melee of defenders.

Villa made a double-change in a bid to freshen up their side, bringing on Petrov and Stewart Downing for Barry Bannan and an exhausted Robert Pires, and began to have more chances on the break as the Blades threw caution to the wind.

Steve Simonsen had to make a couple of first-class saves of his own, denying Petrov with a foot after he had been left one-on-one thanks to Downing's through ball - adding to his first-half full-stretch effort to keep out Agbonlahor.

But Young then saw red to give the hosts renewed hope. Already on a yellow, he had been due to be substituted earlier - but Pires had forced Houllier to change the plans moments from the end. It cost Villa as a poor challenge saw Young pick up a second yellow card.

That invited a swell of pressure from the Championship outfit. Johannes Ertl forced a save from Friedel with an overhead kick, while Elian Parrino and Leon Britton both had half-chances.

But in the dying moments Villa put the tie beyond their opponents when a flowing break culminated in Albrighton laying on a chance for Petrov which the Bulgarian clinically finished.

Houllier pumped his fist at the final whistle, finally showing some emotion as his side came through a tricky afternoon to score an all-important win and book their place in the fourth round.

The Blades, meanwhile, will switch their attention back to avoiding the drop in a disappointing season.