The Whites earned a dominant 1-0 victory over the Hornets at Elland Road on Saturday afternoon, the club's first Premier League victory of the season under head coach Marcelo Bielsa.
Diego Llorente's 18th minute strike was enough to claim all three points though the fixture threw up controversy.
Leeds were denied a penalty by on-pitch referee Simon Hooper and VAR official Lee Mason shortly after taking the lead in West Yorkshire.
Winger Dan James was hauled to the floor by visiting defender William Troost-Ekong as he burst into the box to chase the ball but home protests were waved away.
Watford then saw a goal chalked off in the second half after United goalkeeper Illan Meslier dropped a corner into his own net via Liam Cooper' s back.
The whistle was blown with the ball crossing the line - meaning VAR couldn't intervene - following a tangle between the Leeds skipper and substitute Christian Kabasele.
Replays showed the pair had both been grappling each other but the decision went the way of Leeds and Meslier's goal survived the rest of the encounter relatively untroubled.
The decision, which has split opinion among football supporters, has now been backed by former man in the middle Gallagher.
"I think you need to watch it carefully," he told Sky Sports over the decision to disallow the Watford goal.
"When it happened on Saturday and ended up in the net, my immediate reaction was that the goalkeeper had dropped the ball and the tangle between Kabasele and Cooper had no impact on the goal.
"When you look at it, it does - because when they fall it actually strikes Cooper's back and goes into the goal.
"There's a tangle between the two players and because of that it puts the ball into the net and that's why the referee is forced to disallow the goal. He feels Kabasele has dragged Cooper down.
"There's no doubt they're grabbing each other and it has impacted it - it's gone in off Cooper.
"It strikes him and goes in, so you can't ignore that. He blew his whistle when the ball came across before it went in the net.
"The referee felt Kabasele was more of a fouler than Cooper, if you like. I think it was right to disallow it.
"When I saw what happened with Cooper I changed my mind. My instinct was that the goalkeeper had dropped the ball but when I saw the replay it followed on."
Ex-Leeds captain Stephen Warnock, who attended the game in LS11, disagreed with the ex-top flight match official's verdict.
"I thought it was a goal," Warnock said.
"I think there's enough of a 50-50 challenge between the two players going after each other to just say get on with the challenge between you. I think Leeds and Cooper are lucky.
"Even when Cooper gets up there isn't a complaint from him to say he's been dragged down. It's both ways and they know it."
We’ve gathered the best of today’s Premier League chatter below...
![Midtjylland star Jens Cajuste could still be on his way to the Premier League, with Newcastle United planning a bid in excess of the £12 million they offered in August. (Homme du Match)
(Photo by MIGUEL RIOPA/AFP via Getty Images)](https://www.thestar.co.uk/webimg/b25lY21zOmIxNzM3YTc0LTg4MjItNGRmYy1iM2E2LWEzNDE1ZWJlYjg2NToyYzYxNDY5Ny05NjY4LTRiNWQtYTJjYS0wMTE3OGQzMDYyODE=.jpg?crop=3:2&trim=&width=640)
1. Toon could return for Cajuste
Midtjylland star Jens Cajuste could still be on his way to the Premier League, with Newcastle United planning a bid in excess of the £12 million they offered in August. (Homme du Match) (Photo by MIGUEL RIOPA/AFP via Getty Images)Photo: MIGUEL RIOPA
![Manchester United are keen on a potential transfer deal for Brighton midfielder Yves Bissouma. (Transfer Window Podcast)
(Photo by Clive Rose/Getty Images)](https://www.thestar.co.uk/webimg/b25lY21zOjliMTNlZTIzLThiM2UtNDU2OC1iMThiLTJkMDQ2NDRkN2ZkZjpjN2YxYzA5Yy02OGY3LTQ5MDktYWIwNi1hZDI1NTdlZDljMDI=.jpg?crop=3:2&trim=&width=640)
2. Man United want Bissouma
Manchester United are keen on a potential transfer deal for Brighton midfielder Yves Bissouma. (Transfer Window Podcast) (Photo by Clive Rose/Getty Images)Photo: Clive Rose
![Manchester United and Juventus are set to go head to head for the signature of Ousmane Dembele, who is out of contract next summer. (Mundo Deportivo)
(Photo by Tibor Illyes - Pool/Getty Images)](https://www.thestar.co.uk/webimg/b25lY21zOjI4MDU4N2MyLWNiMjAtNDdlYy1iNjY0LTI3ZjllOWRjNzM5ZDpkZWExNDY3OS00Y2Y1LTQ1MTktOGU4OC05YWQ0Yzk4ODMxYTQ=.jpg?crop=3:2&trim=&width=640)
3. Man United plot Dembele swoop
Manchester United and Juventus are set to go head to head for the signature of Ousmane Dembele, who is out of contract next summer. (Mundo Deportivo) (Photo by Tibor Illyes - Pool/Getty Images)Photo: Tibor Illyes - Pool
![Brentford have entered the race to sign Hammers target Keane Lewis-Potter. West Ham are also keen. (The Athletic)
(Photo by George Wood/Getty Images)](https://www.thestar.co.uk/webimg/b25lY21zOjc2OTI3MzUwLThiNTgtNDM0My1iZTE0LThlNGU2Njg2NTRmYTpiNjcyMTg3Mi1hM2VmLTRlYmUtOWJjNi0xZTRlNWM5ZTk1MGI=.jpg?crop=3:2&trim=&width=640)
4. Brentford eye Lewis-Potter
Brentford have entered the race to sign Hammers target Keane Lewis-Potter. West Ham are also keen. (The Athletic) (Photo by George Wood/Getty Images)Photo: George Wood
![Everton, AC Milan, and Juventus are all interested in signing Donny van de Beek in January to give him a way out of his current situation at Manchester United. (Fichajes)
(Photo by Michael Regan/Getty Images)](https://www.thestar.co.uk/webimg/b25lY21zOjc3NDExN2M2LTMxZmEtNDFkNC1hZDdlLTYzNmMzZmJmMzQwMTozY2M4Y2MxZC05OGVmLTQ1YmMtODNmMi1hZDcxZWJjYzVjZTI=.jpg?crop=3:2&trim=&width=640)
5. Van de Beek in demand
Everton, AC Milan, and Juventus are all interested in signing Donny van de Beek in January to give him a way out of his current situation at Manchester United. (Fichajes) (Photo by Michael Regan/Getty Images)Photo: Michael Regan
![Leeds have been backed to make an offer to sign Derby County star Louie Sibley after the club went into administration recently. (The Athletic)
(Photo by Alex Morton/Getty Images)](https://www.thestar.co.uk/webimg/b25lY21zOmU1ZDZiNzUwLTU5NmMtNGZmZS05YmRlLTkxMDUxMjdmMDVkNDo1OThjZjgyMi0zODFkLTQ5MWItODY2OC1jMzc2OWU1N2JjMjA=.jpg?crop=3:2&trim=&width=640)
6. Leeds linked with Sibley
Leeds have been backed to make an offer to sign Derby County star Louie Sibley after the club went into administration recently. (The Athletic) (Photo by Alex Morton/Getty Images)Photo: Alex Morton