Danny Webber and Darius Henderson scored more than 50 goals in almost 200 combined appearances for the Hornets and both strikers got their names on the scoresheet to give Kevin Blackwell's side a home and away league double against their relegation-threatened opponents.
Indeed, it was Henderson who set up the opener for his strike partner in the 52nd minute by heading the ball back into the six-yard boss from the edge of the area for Webber to turn and fire past Scott Loach after Watford had failed to sufficiently
clear a corner.
And former Manchester United youngster Webber returned the compliment 15 minutes later.
His ball to the edge of the area was touched on by Greg Halford and Henderson got goal-side of Watford skipper Jay DeMerit to lift the ball beyond Loach and double the visitors' advantage.
Henderson will feel he should have made the breakthrough when he was left totally unmarked from a Halford long throw, but Loach made an excellent reflex stop to keep out his header.
This prompted DeMerit and central defensive partner Adrian Mariappa to starting pushing each other amid an inquest into how their former team-mate had been presented with such an easy chance.
The Hornets slowly regrouped after that 13th minute scare and twice should have taken the lead before the break.
First Grzegorz Rasiak saw a free header from a corner kept out by Brian Howard's goal-line clearance and then Jack Cork tried to be too deliberate with a shot after being picked out by Rasiak, giving the Blades the opportunity to block.