The Blades reached this round after seeing off Wrexham at the Racecourse Ground with a 3-2 win. Andy gray cancelled out Craig Morgan's 6th minute lead before Chris Llwellyn restored it for the home side. Blades defender Phil Jagielka made it 2-2 before Gray handed United the win.
Alan Quinn is out as he serves the second of his three match ban whilst Jack Lester is poised to start after Danny Cadamarteri is cup-tied having made his only appearance for Leeds against Swindon in Round 2.
Derek Geary is out for the same reason, he played for Stockport County when they lost 4-1 (aet) at Sheffield United. Alan Wright (stomach) and Simon Francis (knee) are still sidelined through injury.
Possible Blades XI: Paddy Kenny, Leigh Bromby, Phil Jagielka, Chris Morgan, Jon Harley, Michael Tonge, Nick Montgomery, Paul Thirlwell, Andy Liddell, Andy Gray, Paul Shaw.
The Hornets, managed by ex-Blades player Ray Lewington booked their right to be hear by beating Reading 3-0 at the Madejski Stadium. Neil Cox, Hameur Bouzza and an Ivar Ingimarsson own-goal sealed the win.
The visitors however will be without their Captain, Neil Cox who sustained a hamstring injury in the sides 2-2 draw with Ipswich Town.
Cox could be replaced by Jay Demerit in defence but they will also be without Paul Devlin and Brynjar Gunnarsson through injury. Meanwhile Jamie Hand could be handed a place in the 16 man squad after returning from a two month spell at Oxford United.
Possible Hornets XI: Richard Lee, Sean Dyche, James Chambers, Jay Demerit, Jermaine Darlington, Lloyd Doyley, Gavin Mahon, Neil Ardley, Dominic Blizzard, Heidar Helguson, Danny Webber.