Mertesacker said it has had a positive knock-on effect throughout the age groups.
“Mikel (Arteta, manager) gave everyone a powerful message," he told arsenal.com. “I have to say how much it trickled down. I've seen videos of the under-9, under-10 squads cheering Ethan on at Hale End when he came on. Players that would start the same journey as he did, in the grassroots academy, were cheering him on. So all of a sudden he has been escalated to be a role model and a positive influence for young players.
“It's just brilliant to see, that's what we are proud of, that we can show progression, that we can show pathways. It was a very proud moment, first of all for himself and his family. It's a reflection as well of what this club is about, what the academy is about.
“A lot of youngsters entering the academy have the dream of playing for Arsenal Football Club and he made that dream come true. It was a proud moment for us as an academy."
Jack Wilshere, aged 16 and 256 days, was the previous Arsenal record holder when he made his debut against Blackburn Rovers in 2008. Wilshere is now head coach of their under-18 side, the age group that Nwaneri has recently stepped up to.
“We need to give a lot of credit to everyone at Hale End," Wilshere said. “Everyone that's helped him and supported him over the years. There are some people who are really proud, and I'm one of them, but I've been around for a couple of months, and a little bit last season.
“So let's thank everyone down at Hale End for their support and their hard work. Now he's part of my team, one of my players, so I will give him all the support and guidance he needs."