Troy Deeney was at his devastating best during the first half against Huddersfield Town and his goal – his 12th in the last 12 home matches – means Watford currently lead 1-0 at half-time.
Fernando Forestieri had already seen a goal ruled out for offside when Deeney gave the Hornets the lead on 15 minutes when he calmly slotted past Alex Smithies from the corner of the area following a fine pass from the impressive Daniel Tozser.
The Golden Boys, who made nine changes, had several excellent chances during a first half they dominated.
Huddersfield did have a positive spell midway through the half and James Vaughan had a goal ruled out for offside following a fumbled save by Heurelho Gomes.
But Watford were good value for their lead and should be ahead by a greater margin.
Watford line-up: Gomes: Tamas, Ekstrand, Angella; Anya, Munari, Tozser, Abdi, Pudil; Forestieri, Deeney.
Subs: Bond; Andrews, Paredes, Vydra, Dyer, Ighalo, Hoban.
Huddersfield Town line-up: Smithies; Dixon, Lynch, Wallace, Robinson; Butterfield, Coady; Bunn, Majewski, Scannell; Vaughan.
Subs: Murphy, Ward, Hammill, Stead, Sinnott, Wells, Crooks