City manager Pep Guardiola made seven changes to the side that started Sunday’s 3-0 Premier League (PL) win at Crystal Palace, while the Bees’ line-up showed six alterations to the one that began the 1-1 draw with Leeds United that same afternoon.
Oscar Bobb was among those to come in for the hosts and he had the first opportunity when he cut inside and fired straight at Hákon Valdimarsson after 14 minutes.
The young winger limped off with an injury moments later, Phil Foden replacing him, and Abdukodir Khusanov could have joined him in the dressing room, but the City centre-back escaped with a booking for bringing down Kevin Schade as the Brentford striker raced through on goal.
The hosts were hunting a sixth consecutive home win in this competition and they took a big step towards that with the opening goal 13 minutes before HT.
Valdimarsson punched a corner straight to Rayan Cherki on the edge of the area, and the midfielder took a touch before smashing an unstoppable shot into the top corner to make it 11 goal involvements this season (G4, A7).
Brentford had not scored an away goal from open play in any competition since their 5-0 rout of Grimsby Town in the previous round back in October, but defenders Kristoffer Ajer and Michael Kayode both forced James Trafford into saves early in the second half.
Valdimarsson then showed great reflexes to keep out Foden’s snapshot, but the Bees goalkeeper could do nothing about City’s second goal in the 67th minute.
Savinho carried the ball to the left edge of the box and his shot deflected off the sliding Ajer, sending it looping over Valdimarsson and into the net for the winger’s second goal of the season, with both coming in the Carabao Cup.
City saw out the game with little fuss to keep alive their hopes of winning this competition for the ninth time. Brentford, though, have now lost their last five away matches - failing to score in four of those - and face an important PL trip to rock-bottom Wolves on Saturday.
Flashscore Man of the Match: Rayan Cherki (Manchester City)
