Leeds saw their gap over Everton closed to just two points prior to kick-off, meanwhile, Watford's gap to the Toffees and safety had increased to six.
For Watford that gap would remain after the final whistle.
Roy Hodgson named an unchanged line-up from the Liverpool match last weekend, where the Hornets put up a decent display at Anfield, but there was no such positives to take after what was another frustrating home performance at Vicarage Road.
From that point onwards, the Hornets early intensity in attack appeared to fade for the remainder of the first half, with the visitors also just happy to get to the break ahead.
In the second half, Watford did have a go, getting plenty forward in attack, however, despite a really good chance for Ismaila Sarr to make it 1-1, the Hornets never really threatened Meslier's goal.
Naturally, with Watford committing more men forward, gaps opened up for the visitors to exploit, but it was poor Hornets defending that would see this game put out of their reach.
Poor defending from first Hassane Kamara and then Samir gifted Rodrigo the ball and unlike Watford had been able to do through Sarr, he coolly took the opportunity.
Harrison would later add a third for the visitors, sealing three points that will surely see the Yorkshire club remain in the Premier League.
One foot in the Championship
Watford seem destined for relegation, with their ninth consecutive home defeat meaning the Hornets already have one foot in the Sky Bet Championship.
The gap to Everton is currently six points, but with the Toffees also having a game in hand over the Hornets, this gap could be extended to as many as nine.
If Watford had any chance of survival, their next three home matches, including today, were crucial, and not for the first time this season, the Hornets failed to deliver at home.
Vicarage Road stood half empty by the time the full-time whistle was blown, with most Watford fans accepting their fate at this stage.
Roy Hodgson said after the game that not much had changed in terms of the challenge ahead for his side, but with performances like today, the Hornets will not come close to Premier League survival.
Costly individual errors
Once again today, an individual error contributed to the Hornets' downfall.
At 1-0, Watford were pushing hard for an equaliser, but a lapse of concentration and quality gifted Leeds a second goal and put the game beyond the Hornets.
Today, it was Samir and Hassane Kamara at fault.
For the first goal, it was Samir's poor clearance that gifted Raphinha a shot on goal, from which he would score.
After the Brazilian defender had attempted to clear his lines, Dan James beat Juraj Kucka to the loose ball, finding Raphinha with the pass, whom Samir had lost in the process of clearing the ball.
The Leeds winger fired home from distance.
Samir was once again involved in the second Leeds goal for all the wrong reasons, along with Kamara.
A mix up at the back between the two allowed Rodrigo the ball, with the Spanish forward left to run past Foster and slot the ball into an open net.
It was the goal that put the game beyond the Hornets, and it was a somewhat fitting way to concede, given it was due to individual errors, something that has plagued them all season long.
Where do Watford go from here?
At the time of writing, Watford remain 19th in the Premier League and six points from safety with just seven games remaining and it's hard to see where the Hornets go from here.
It's Brentford up next, followed by Manchester City away and then Burnley at home. Six points from the Brentford and Burnley fixtures is surely essential if Roy Hodgson's side have even a glimmer of hope of survival.
At this point though, it is looking an uphill battle for the Hornets.
Whilst Roy Hodgson and the players must continue to fight, the club hierarchy must surely start planning for life in the second-tier.
That includes the search for a new head coach for next season, with Roy Hodgson at the club only on a short-term basis.
With plenty of incomings and outgoings to be done, whoever the next man in the dugout is at Vicarage Road, they have a big job on their hands.