Looking to bounce back from their disappointing draw at Everton last time out, City aimed to make a fast start, and Doku forced Caoimhim Kelleher into a low save inside the first three minutes. Haaland also had chances, first heading over before nodding straight at Kelleher and then having a shot blocked by Nathan Collins.
Buoyed by their first-half performance, Brentford began to create opportunities of their own after the break, and Gianluigi Donnarumma had to be at his best save from Igor Thiago. City, however, would not be denied, and Doku produced his third stunning finish in the space of a week as he cut in from the left and curled a shot into the top corner of Kelleher's net.
The title-challengers then looked to make the game safe, and soon after substitute Phil Foden had a shot saved by Kelleher, Haaland managed to force the ball over the line with a close-range backheel in the wake of Brentford failing to clear Antoine Semenyo's ball across the box.
Foden was denied again by a spectacular Kelleher save before Marmoush ran onto Haaland's through-ball in stoppage time to complete the victory for the treble-chasers.
GOAL rates City's players from the Etihad Stadium...
