With City not in action until Wednesday evening, Jose Mourinho's side had a chance to put some pressure on the title favourites and did so as they eventually ran out 4-2 winners in Hertfordshire.
It was by no means a straightforward win, however, with substitute Troy Deeney and Abdoulaye Doucoure bringing Watford within sight of a famous comeback before Lingard's fine solo goal settled matters.
The Special One could not believe his eyes his wing-back found his first Premier League goals since a defeat or Bournemouth back in May 2016.
And against his former club, the 32-year-old delivered a masterclass of a performance in the first half.More news: The most adorable revelations from Prince Harry and Meghan Markle's first interview
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Marco Silva's Watford hit the bar through Richarlison, but never looked like recording a second successive home win over the Red Devils.
The first time they successfully fed the Belgian, he played in Lingard, whose pass to Young was thrashed home by the former Watford man to give the visitors the lead.
England worldwide Lingard scored a tremendous solo goal in the 86th minute to sting the Hornets, who set up a tense finale by rallying from three goals behind with just 13 minutes remaining.
Christian Kabasele did not get enough purchase on a clearing header and Lukaku intelligently volleyed the ball into the path of Martial, who adroitly steered a low shot past Heurelho Gomes.
United suffered an apparent injury blow as Nemanja Matic limped off the pitch in the 55th minute and was replaced by Ander Herrera.