The grandstand finale looked a distant prospect as Brentford trailed to Reiss Nelson’s eighth minute goal and did little more than go through the motions during a tepid first half. But this Carabao Cup third-round tie heated up after the hour mark and Arsenal would be indebted to the goalkeeper Aaron Ramsdale and some robust defending from those in front of him. Mikel Arteta started Ramsdale ahead of David Raya, his new No 1, who is on an initial loan and was available for selection here, Brentford having indicated they would have no problem with facing him. The home crowd goaded Ramsdale, making it clear they considered him to be inferior to Raya – or words to that effect. But Ramsdale had the last laugh, making an excellent fingertip save to push Yoane Wissa’s 66th minute shot against the inside of the post and away. Ramsdale would celebrate with a double fist pump towards the fans behind him and he could also reflect on a decent save later on from Frank Onyeka’s long-ranger. Brentford got bodies forward and loaded high balls into the box but Arsenal held firm, advancing to the last 16 of a competition that feels open after Manchester City’s defeat at Newcastle. Arteta had a clutch of high-profile injuries, including Declan Rice, Bukayo Saka and Gabriel Martinelli, and he made wholesale changes from Sunday’s derby draw against Tottenham. As needs must, with Champions League football swelling the schedule. There was a debut for the 19-year-old Charles Sagoe Jr on the right wing but it was the player on the other flank who made the difference, Nelson finishing calmly after a disastrous Brentford sequence. It was a loose back pass by Mathias Jorgensen to Eddie Nketiah and, when the Arsenal striker crossed low, Nathan Collins failed to cut it out when he looked the favourite to do so. It was Nelson’s first goal since his winner against Bournemouth in March. Thomas Frank had injuries, too, but he went with virtually his strongest available XI – as much as anything to try to get a reaction to Saturday’s home defeat against Everton. If it was not Brentford’s worst performance since their promotion to the Premier League, it was on a list of two with Burnley away in October 2021. It felt as though the hangover still pounded during an intensity-free first-half performance from them; there was little tempo and no pressure on the ball. Vitaly Janelt had a snapshot blocked and there was a clear chance for Wissa on 35 minutes from a Christian Norgaard cross only for him to drag woefully wide. Arsenal were comfortable, playing their first-time passes, and they might have had another goal by then. Emile Smith Rowe, making his 100th Arsenal appearance, glided through after a one-two with Jorginho to work Mark Flekken while Kai Havertz took too long when well-placed, seeing his shot blocked. The stadium announcer had urged the home fans to “get those vocal cords ready to go” for the second half and they responded, the Brentford players feeding off the increased energy. They pushed higher and showed their physicality, including in the area on long throws from the substitute Mathias Jensen. An equaliser did not seem unthinkable now and Wissa was so close to it, Ramsdale enjoying his moment with the big save. Nelson and Nketiah would go close to extending Arsenal’s lead on the break but it was more important to keep Brentford out. “It became a difficult game for us,” Arteta said. “When you don’t play that well, you have to have some big defensive moments. Ramsdale was exceptional. We love him for sure.”