Mikel Arteta had no doubt Aaron Ramsdale would perform when called upon after the goalkeeper kept Brentford at bay.
Reiss Nelson's early goal secured a 1-0 victory at the Gtech Community Stadium to send Arsenal through to the fourth round of the Carabao Cup.
But it was two fine saves from Ramsdale in the second half which denied the Bees the chance to get back into the match.
Ramsdale had sat out the last three matches, including Sunday's north London derby draw against Tottenham, with Arteta preferring David Raya, the summer signing from Brentford.
The Gunners fans sung his name before kick-off and Arteta said: 'For sure, he's been exceptional around the place and especially with the situation.
'We love him, for sure. We know his character and what he brings to the team and we are happy to have him. Every player is very important. Today he had the opportunity to play and he had a really good game.
'I'm really happy. It was two very different halves. In the second they had a more aggressive approach and we were too direct and it became a difficult game.
'When we don't play that well you need some big blocks in the box and we did that.'
The winning goal came 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 improved after the break but were frustrated when Ramsdale tipped Yoane Wissa's snap-shot against a post, and then aimed a fist pump at the home fans behind the goal who had been giving him stick.
'I didn't see the second part, but I saw the first. It was a great save and crucial for us to winRead on m.allfootballapp.com