Beattie benefited from a fortunate rebound for his first goal, a questionable piece of goalkeeping for the second, and slack marking for the third, but his predatory instincts were clear for all to see.

Leicester chose five defenders in the absence of the ineligible Lee Hendrie, on loan from United, but they had few answers to former England striker Beattie, who has now scored 19 of the Blades' 46 league goals this season.

Veteran Ugo Ehiogu was chosen to replace United's suspended captain Chris Morgan in the heart of defence, and goalkeeper Paddy Kenny was unable to make the start, so Ian Bennett stood in between the sticks.

The Blades were ahead inside 12 minutes in contentious circumstances.

Beattie did well to flick on a long ball for his strike partner Billy Sharp, who went over under the close attentions of Patrick Kisnorbo.

The Australia defender was the last man and, after consultation with his assistant, referee Mike Pike showed Kisnorbo a red card.

Beattie's penalty was well parried by Paul Henderson, but the rebound fell kindly for the striker who made no mistake second time around.

Two minutes later the lead was doubled when Richard Stearman felled Sharp 20 yards from the Leicester goal.

Beattie's speculative free-kick bounced before it reached Henderson's goal but the Foxes goalkeeper should have done better.

After 17 minutes Beattie completed his hat-trick when Michael Tonge swung in a corner and he lost his marker to power a header past Henderson.

The unfortunate Stearman was never far from trouble, and he was booked two minutes later for a foul on Stephen Quinn.

Steve Howard had Leicester's first sight of goal after 41 minutes but his long-range shot flew over.

It was almost 4-0 just before the break when Tonge floated a ball over for Matthew Kilgallon but his header missed the target.

Howard made clear the Foxes' intentions when he let fly just 22 seconds after the restart, but Bennett saved easily.

Beattie almost grabbed his fourth 10 minutes after half-time but he could not turn Quinn's cross home.

Tonge again caused Henderson problems from a corner, and the Australian goalkeeper was forced to punch away uncertainly.

Exasperated manager Ian Holloway brought on James Chambers and Andy King just after the hour to try to prevent further damage, but United continued to search for a fourth.

Beattie's final attempt to add to his tally was unsuccessful, and with his work done he was withdrawn for Jonathan Stead.

Leicester finally carved out a meaningful opportunity when Matty Fryatt shot from inside the area, but Bennett saved well.

Stead, seeking his first Championship goal since October, was thwarted by a diving Henderson with six minutes left, and the Blades had to be content with Beattie's first-half heroics.