Watford head coach Marco Silva's anger was palpable after Bristol City inflicted a "really bad'' Carabao Cup second-round defeat on the Premier League side.
Given the Hornets' solid start to life under the Portuguese and the Championship visitors' nine changes, few would have predicted the unfancied Robins emerging victorious at Vicarage Road.
A dire opening period was forgotten when Etienne Capoue put Watford ahead early in the second half, with City soon hitting back through 18-year-old Freddie Hinds and substitute Bobby Reid.
Watford left-back Jose Holebas saw red before City's Niclas Eliasson scored as matters were compounded for the hosts, whose fans had headed for the exit by the time Adrian Mariappa scored a consolation late in the 3-2 defeat.