Nicky Shorey appeared to handle an injury time goalbound effort from Tom Cleverley that was heading into the empty net. Referee Andy D'Urso waved away claims from Watford leaving boss Malky Mackay dumbstruck.
Mackay said: "I think myself, the fourth official, their bench, 15,000 people and the boy himself (Shorey) - who admitted it to one of the players afterwards - saw the hand go from down by his side to up near their (by his head) and stopped the ball going into an empty net.
"I've seen it six times (on the video) but the first reaction is always the one that you look at to start with and it was amazement.
"Everyone was exactly the same and I think when so many people are amazed then it's usually the case."
Watford now look to build on this point when they travel to Bristol City on Monday.