The forward produced another stunning display at Vicarage Road.
The Jaguars are looking for their first win of the season against the Dolphins who are aiming for victory number two of the campaign in Tottenham.
Sadio Mane also netted for the Reds.
Firmino’s hat-trick and Salah’s scorcher lead Liverpool rout of Ranieri’s Watford Roberto Firmino celebrates scoring Liverpool’s third goal as Mohamed Salah runs to celebrate and Ben Foster looks on forlornly. Photograph: John Powell/Liverpool FC/Getty Images