Manager Micky Adams recalled striker Darius Henderson and midfielder Lee Williamson to his starting XI against their former club, but was left to regret his decision as the former Hornets pairing both saw red in the space of six minutes.
Striker Danny Graham had already put the home side ahead after some dreadful defending gifted him his 23rd goal of the season and second-half goals from Martin Taylor and Ross Jenkins made sure.
Watford announced this week they are on the verge of a takeover by a group led by entrepreneur Laurence Bassini, and keeping hold of Graham is likely to be top of the new chairman's wishlist.
The visitors, however, will struggle to keep any of their top players if they are relegated to npower League One. Defeat left the Blades six points from safety with nine games remaining.
Source: PA
Source: PA