While the Gunners received a bye to this stage of the tournament, Thomas Frank's side had to survive a scare to overcome Newport County on penalties in the second round.
Returning to haunt his former club, Everton defender James Tarkowski was the architect of Brentford's downfall during Saturday's Premier League showdown, as the Toffees came away from the English capital with their first top-flight win of the season - much to the home crowd's disbelief.
Mathias Jensen had originally cancelled out Abdoulaye Doucoure's opener with a fine strike across Jordan Pickford's goal, but Tarkowski rose highest to meet a corner in the second half, before Dominic Calvert-Lewin banished his recent injury woes with a third for the Toffees.
Everton walked away from the Gtech Community Stadium as only the third team to beat Brentford at their headquarters since the turn of the year, but home draws with Tottenham Hotspur, Bournemouth and Crystal Palace represented a mediocre start to another top-flight campaign for the Bees, who are 13th in the rankings with just a solitary victory to their name.
Jensen's consolation at least managed to stretch Brentford's goalscoring streak at the Gtech to 14 games since another London derby knockout exit - losing 1-0 to West Ham United in a January FA Cup tie - but a giant killing was nearly on the cards at Rodney Parade last month, only for Brentford to break Newport hearts from the penalty spot.
That 12-yard success saw Frank's side overcome a significant psychological hurdle, as they fell to a third-round defeat to Gillingham from spot kicks last year, prior to which they had reached the EFL Cup quarters in 2022 and played a historic semi-final in 2021, losing to Tottenham Hotspur.
Seeking to prolong Brentford's recent run of disheartening cup results against their London rivals, Arsenal have a couple of points to prove in the wake of a captivating 2-2 North London derby draw with Tottenham Hotspur, who came from behind twice at the Emirates to snatch a share of the spoils.
Cristian Romero was the villain in his own area on more than one occasion - deflecting a Bukayo Saka strike into his own net before giving away a penalty for the Englishman to stroke home down the middle - but on both occasions, James Maddison set up Son Heung-min to peg the Gunners back.
By taking a point home from their arch-rivals' territory, Ange Postecoglou has already achieved a feat that none of Nuno Espirito Santo, Jose Mourinho or Antonio Conte managed, while Mikel Arteta was left to rue untimely injuries to key players and an individual error from Jorginho which gifted Tottenham their second goal.
While there was a palpable sense of frustration, the Gunners' unbeaten record this season is still intact, but the two-time EFL Cup champions - who have not lifted the trophy aloft since 1993 - lost at the first hurdle to Brighton & Hove Albion in the most recent edition.
Arteta's side were also forced to accept a point in their most recent showdown with Brentford - a contentious 1-1 draw at the Emirates which saw the Bees' equaliser wrongly given despite Christian Norgaard being in an offside position - but their only previous EFL Cup meeting ended with Arsenal easing to a 3-1 win under Unai Emery in 2018.
The injuries have been piling up for Brentford over the past couple of weeks, as straight after losing Rico Henry to a devastating knee problem - which could rule him out for the season - Kevin Schade tweaked a groin muscle while taking a shot during the warm-up at the weekend.
Schade is now confirmed to be missing for months as he prepares to undergo surgery, and he joins Henry, Shandon Baptiste (shoulder), Ben Mee (muscle), Mikkel Damsgaard (groin) and former Arsenal prospect Josh Dasilva (hamstring) in the Bees' treatment room.
Rumoured Gunners target Ivan Toney has only served half of his eight-month ban, and Neal Maupay - who could not face his parent club at the weekend - is now cup-tied, having represented Everton in their second-round win over Doncaster Rovers.
Arteta can empathise with Frank when it comes to growing injury lists, as the Spaniard was forced to take off Declan Rice midway through the North London derby owing to a back concern, while Leandro Trossard was a last-minute absentee due to a muscular problem sustained in training.
Bukayo Saka was also moving gingerly as he came off towards the end of the game, while all of Thomas Partey (groin), Jurrien Timber (knee) and Gabriel Martinelli (hamstring) remain out of contention - the latter has also missed out on a place in the latest Brazil squad.
Having seemingly been demoted to second choice, Aaron Ramsdale will be given a run-out in between the sticks as David Raya cannot play his parent club, while Reiss Nelson, Emile Smith Rowe, Takehiro Tomiyasu, Cedric Soares and the fit-again Mohamed Elneny are in line for a rare start too.
Brentford possible starting lineup:
Strakosha; Roerslev, Zanka, Ajer, Hickey; Onyeka, Janelt, Ghoddos; Lewis-Potter, Mbeumo, Wissa
Arsenal possible starting lineup:
Ramsdale; Cedric, Saliba, Kiwior, Tomiyasu; Havertz, Elneny, Jorginho; Nelson, Nketiah, Smith Rowe
We say: Brentford 1-2 Arsenal
Even with a growing list of injury concerns and a raft of changes expected on Wednesday, Brentford can almost always be relied upon to make the net bulge at the Gtech, where a surprise result is not beyond the realm of possibility versus a second-string Arsenal side.
The EFL Cup will not be high on Arteta's priority list this season, and some fans may - in hindsight - claim that an early exit will be a blessing in disguise, but a much-changed Gunners team can still capitalise on Brentford's fitness woes and defensive deficiencies to progress to round four.
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