Nick Blackman, Dave Kitson and Shaun Miller struck for the Blades, who are two points clear of Tranmere in second.
Tranmere Rovers kept up the pressure with a come-from-behind win over Crewe Alexandra, with Adam McGurk and Max Power overturning Bradden Inman's goal in a 2-1 win.
Will Grigg scored twice as Walsall secured a League One double over high-flying MK Dons with a 4-2 win.
Grigg's brace plus goals from Febian Brandy and Jamie Paterson handed the Saddlers a second successive win, while Ryan Lowe and Dean Bowditch were both on target for the below-par Dons.
Lewis Grabban scored his seventh goal in as many games as play-off chasing Bournemouth thumped Yeovil 3-0 at Dean Court.
A goal in each half by Grabban and Harry Arter, prior to Brett Pitman's late penalty, earned the Cherries a 12th win in a remarkable run of 14 unbeaten matches.
A 91st-minute strike from Dave Syers earned Doncaster a 2-1 win at Oldham which keeps them fourth. The visitors took the lead at Boundary Park early through Rob Jones, only for Youssouf M'Changama to level before the half-hour mark.
Brentford stretched their unbeaten league run to 10 matches with a 3-1 win at struggling Colchester.
Preston's winless league run at Deepdale continued after the Lilywhites drew a blank in a goalless draw at home to north west rivals Bury.
Shrewsbury rescued a useful point with a late equaliser to frustrate promotion hopefuls Notts County after an entertaining 2-2 draw at Greenhous Meadow.
Nicky Adams and Billy Clarke strikes helped Crawley come back from a goal down to beat Portsmouth 2-1.
Stevenage were humbled 3-1 at home by Coventry City, meaning that Swindon remained ahead of them despite their own fixture with Leyton Orient being postponed because of a waterlogged pitch.
More to follow