Burnley boss Steve Cotterill thought the introduction of second-half substitute Gifton Noel-Williams turned the tide in favour of the Clarets, who at that time were hanging on to a 2-1 lead.
After a dull opening half hour a fine individual goal from Graham Branch put Burnley in front as he seized on a mistake by Clarke Carlisle and after galloping fully 40 yards, slotted the ball past keeper Ben Foster.
It was Foster who contributed to Burnley's second goal and he was penalised for handling the ball outside his area by an eagle-eyed assistant referee.
And the Hornets were made to pay for Foster's personal mistake as Burnley left-back Jon Harley converted the free-kick from just outside the box.
A double substitution by Watford boss Adrian Boothroyd had the desired effect with Marlon King pulling a goal back with a fine strike from 25 yards for his 12th league goal of the season.
Burnley were then indebted to a fine double save from keeper Brian Jensen to foil efforts from Matthew Spring and Carlisle.
But it was the introduction of Noel-Williams that finally meant that the Clarets could breathe easily.
From a Harley corner Noel-Williams saw his header cleared off the line by Paul Devlin, but the Clarets didn't have to wait long before they got their third goal.
With the Watford defence again contributing to their own downfall as hesitation between Lloyd Doyley and Foster was seized on by Branch, with the Burnley midfielder then being upended by the Watford keeper.
Harley successfully converted the resultant spot-kick for his second goal of the game and a rampant Clarets scored again just two minutes later with Noel-Williams the provider and James O'Connor supplying the finish.