It was a Bruno Fernandes show on the pitch tonight, as the January signing scored the opening goal and laid on the assist for their third goal scored by Mason Greenwood.
Anthony Martial scored an absolute stunner in the 58th minute to double their lead after being dreadful throughout the first-half, while Watford captain Troy Deeney's goal was rightly disallowed by VAR a few minutes earlier.
The visitors looked the better side in the early stages of the game but lacked that edge going forward and Fernandes' goal late in the first half tuned out to be the fatal blow to their spirit and it seemed they never recovered from that shock, as they failed to match United's intensity after the play resumed in the second half.
So, as the Red Devils kept yet another clean sheet in the top-flight, here are the top performers and the flops from tonight's game.
In the first 45 minutes of the game, both sides were very much into the game and honestly, the visitors looked the more determined side from the get-go.
Though there were not any extraordinary performers from both sides until Bruno Fernandes earned the penalty in the 41st minute, there were two players from the home side who were frustrating to watch and committed a lot of errors, they were Anthony Martial and midfielder Fred.
Martial redeemed himself with a wonderful goal in the second half, showing the amount of potential he possesses, but it was Fred who continued to disappoint.
The Brazilian who signed for the club in the summer of 2018 for £52 million fees, has emerged as one of the first names on the sheet under Ole Gunnar Solskjaer but is yet to find his feet.
In the fixture, he was dispossessed way too often and was targeted by opposition players, especially Troy Deeney who closed him down and won the ball back on multiple occasions in the first half.
If not for the lack of decisiveness from Watford in the final third, his mistakes could've ended up costing them a goal in the 32nd minute, as Doucoure's shot was saved by De Gea.