Turns out Morata can play, and his diving header met a classy bit of playmaking from Willian to make it 3-1 in the 69th minute.
A second yellow card for Cesc Fabregas in the 81st minute of the game led to his being sent off.
Chelsea are expected to make new signings before the end of the transfer window with British media reporting that Conte is dissatisfied with the depth of his squad. Chelsea are also without Eden Hazard, Pedro and Tiemoue Bakayoko, who are all injured, and they sold Nemaja Matic this summer to Manchester United.
The Terriers were the better side and got the goals to prove it, with record signing Steve Mounie striking twice after Joel Ward's own goal had given David Wagner's side the lead.
Soon after, Vokes had a goal called offside.
But Liverpool came out fighting after the break, and grabbed an equaliser 10 minutes into the second half after Watford keeper Heurelho Gomes brought down Mohamed Salah in the area.
In the 3pm kick-offs, champions Chelsea were predicted to start their campaign with an easy win over Burnley at Stamford Bridge, only for Antonio Conte's men to find themselves 3-0 down at half time.
Standing in their way of starting the new season in style is a Clarets side which won just once on their travels last season - in the penultimate away game against Crystal Palace - and have been weakened by the departures of Michael Keane and Andre Gray. The Chelsea supporters vented their anger towards referee Pawson, while the delirious Burnley fans sang: "We are top of the league!"