United are short of centre-backs as Chris Morgan is out with a hamstring strain and Kyle Bartley suffered a fractured cheekbone in midweek.Boss Gary Speed, who is without banned striker Jamie Ward, could play Johnny Ertl alongside Nyron Nosworthy or Ritchie De Laet at the back.
Watford manager Malky Mackay has a fully-fit squad available.
Young defender Dale Bennett has recovered from an ankle injury and is back in contention.
MATCH PREVIEW
After a three-match winning run, Watford were brought down to earth when Swansea, managed by former Hornets boss Brendan Rodgers, beat them 3-2 at Vicarage Road in midweek.
But their recent form and away record means they can still head to Yorkshire full of confidence. Watford are the only team unbeaten away from home in the Championship this season, apart from leaders Queens Park Rangers.
Like QPR, Watford have picked up 10 points on the road this season. And no second-tier team has netted more goals away from home than Malky Mackay's side, who have scored 11 so far.
Sheffield United, on the other hand, have scored only five times this term - giving the Blades the bluntest attack in the division. But they have shown signs of promise since the appointment of manager Gary Speed, and a win on Saturday would be their fourth in seven league matches.
MATCH FACTS
Head-to-head
• Watford have picked up a solitary point from their four visits to Sheffield United since a 4-1 win there in February 2006.
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• The winner of the last three clashes between these clubs has kept a clean sheet.
Sheffield United
• United have failed to score in all four of their league defeats this season.
• Their Championship matches this season have produced fewer goals than any other club's (16; five for, 11 against).
• Stephen Quinn could make his 150th appearance for the club, while Ched Evans may make his 100th career appearance.
Watford
• Watford have picked up five more points away than at home this term - the widest such disparity in the Championship.
• The Hornets have scored 11 goals in their last three league games.
• They have scored 10 first-half goals this season - more than any other team in the second tier.
• Watford have five players who have been on the field for every minute of their nine Championship matches - more than any other club.
• Danny Graham is set to make his 200th career league appearance.
Source: BBC Sport
Source: BBC Sport