Mohamed Salah was brought down in the box by an onrushing Heurelho Gomes.
Watford will now be looking to build on their opening-day draw when they take on Bournemouth at the Vitality Stadium next week, with Britos, the scorer of their late equaliser, admitting that the they must learn from the mistakes they made against Liverpool. "Clearly, in terms of defending corners, and we talk about second phase...you have got to look at the distance the ball is cleared before you then start coming out of your position".
Marco Silva's first game in charge of Watford ended with a draw and the Portuguese boss will have seen plenty of positives, while the same defensive issues continue to plague Klopp's Liverpool.
To their credit, the visitors turned the game on its head before the hour mark.
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However, Watford were soon in front once again when Abdoulaye Doucoure fired home to make it 2-1 to the home side at half-time.
Ten minutes into the half, Liverpool got their something.
Salah's pacey runs threatened Watford and he came close to making it 4-2, missing the crossbar by less than a yard.
Watford had the stuffing knocked out of them and Liverpool nearly grabbed a fourth with Alberto Moreno's powerful drive pushed over the bar by Gomes.
The Hornets twice led at Vicarage Road, but they went into stoppage time trailing 3-2, before defender Miguel Britos popped up with a timely equaliser.