Both sides tried their best, creating a total of 27 attempts, with the bulk of them falling to Watford, but this was to be a good day for both keepers.
Aston Villa's Thomas Sorenson made the more eye-catching stops, including one tremendous reflex effort to deny Malky Mackay, but his opposite number Ben Foster had to go full-length to deny Gabriel Agbonlahor and also race smartly off his line on a couple of occasions to thwart Stilian Petrov, who pulled the strings in the opening period.
Watford and Villa were both unchanged but neither side was able to make the breakthrough in an end-to-end first-half that simmered nicely without ever exploding into full life.
It was Villa who started the better with Steven Davis testing Foster with an early drive before the England keeper had to make a better save to deny Petrov after Olof Mellberg had found the Bulgarian on the right side of the penalty area.
Davis then went close with an angled drive that flashed narrowly wide of the far post.
It wasn't all one-way traffic though, as Dan Shittu's knee deflected a Watford cross wide and Mackay headed over, but the visitors' quick, often one-touch, counter-attacking was increasingly catching the eye.
An offside flag prevented Petrov having a clear scoring opportunity after some incisive build-up play around the Hornets' area involving Juan Pablo Angel, and then Agbonlahor's blistering pace took him clear of Jordan Stewart down the Watford left flank, but Foster made the save.
Although Sorenson had to tip a Shittu header that was going behind anyway away for a corner, it was Villa who held the attacking ascendancy going into the interval.
An astute piece of defending from Mackay prevented Angel pulling the trigger in the area after Luke Moore had knocked the ball back, and then Foster was again quickly off his line to thwart Petrov after another neat one-touch move, again involving Angel.
Boothroyd decided changes were needed at the break, and on came Jay DeMerit and Hameur Bouazza for Lloyd Doyley and the ineffective Darius Henderson, but the pattern of the game stayed the same, only to step up in intensity.
Villa had the early momentum with Foster saving an Agbonlahor drive and then Angel blazed a cross from the right horribly over.
The Colombian striker could also have scored when he was picked out by a Davis centre from the left, only to head wide from eight yards.
But Watford's response to those escapes was impressive. First, Sorenson got down well to keep Bouazza's stinging effort from the edge of the area out and then the Dane made an even better save, arching his back to turn away Marlon King's fiercely-struck angled volley on the turn.
However, Sorensen's third stop in a five-minute spell was to be truly exceptional. Mackay must have thought he'd scored when his head connected superbly with Ashley Young's corner to the far post from six yards out, only to see the ball kept out by the keeper's reflex save.
King wasn't far wide with a placed effort from the edge of the area as the attacking momentum stayed with the home side into the closing stages, but the one golden opportunity they craved was to elude them.