By SABC Sport
27th September 2023
Nelson's first-half goal, after some dreadful Brentford defending, was enough to send the Gunners through to the fourth round.
Ramsdale was handed a recall after being dropped in favour of David Raya, who joined from Brentford this summer.
Raya had started Arsenal's previous three games, including Sunday's north London derby against Tottenham, displacing Ramsdale after 52 consecutive Premier League games.
With Bukayo Saka and Declan Rice injured against Spurs to join Thomas Partey, Gabriel Martinelli, Leandro Trossard and Jurrien Timber on the sidelines, Mikel Arteta made eight changes in total.
The visitors took the lead after only eight minutes thanks to a mistake by the recalled Mathias Jorgensen, whose pass back wrong-footed Ethan Pinnock.
Eddie Nketiah leapt on the error, cutting the ball back for Nelson who stepped past a sliding Nathan Collins before neatly finishing past Mark Flekken.
Brentford were flat for long periods of their home defeat by Everton in the Premier League on Saturday and this was more of the same in the first half.
They would have been two down after half an hour but for the outstretched leg of Flekken which denied Emile Smith Rowe a goal.
The Bees look as though they are starting to miss their striker Ivan Toney, who is still suspended for admitting breaches of gambling rules and is likely to be an Arsenal target when he is available again in January.
But they eventually began to get forward and Vitaly Janelt's shot was blocked by the diving Takehiro Tomiyasu.
They almost equalised when captain Christian Norgaard beat Kai Havertz in midfield and crossed for Yoane Wissa, whose first-time shot flew just wide.
There was a wobbly moment for Ramsdale when he was almost caught in possession by Wissa, but the ball ran away from the Bees frontman.
But the keeper came up with a fine save midway through the second half, pushing Wissa's snap-shot against the far post.
Nelson could have had a second when Havertz got clear down the left and played the ball across, but his shot clipped the outside of Flekken's post.
Flekken saved well from Nketiah at his near post before Ramsdale flung himself to his left to beat away Frank Onyeka's drive as the Gunners held on.