It was the moment Myles Lewis-Skelly must have been dreaming about all of his young life. Making his full Champions League debut at left-back because of a defensive injury crisis, the 18-year-old born in Islington and raised in Arsenal’s Hale End academy for the past decade could easily have panicked when he was confronted by a charging Eliesse Ben Seghir just after the half-hour mark.

What he did next was absolute validation of Mikel Arteta’s decision not to recall 27-year-old Kieran Tierney for a victory that should go a long way to confirming that Arsenal qualify in the top eight of the new Champions League format. Neatly sidestepping the advancing Monaco forward, who at 18 months his senior was the next youngest player on the pitch, Lewis-Skelly penetrated the visitors’ defence with a piercing throughball that allowed Gabriel Jesus time and space to set up Bukayo Saka for the easiest of tap-ins at the back post.

All of Arsenal’s players rushed to congratulate not the goalscorer but rather the architect of their breakthrough, with Saka reserving an extra big hug for the youngest Arsenal player to start in this competition since Alex Oxlade-Chamberlain in 2011. Who needs a technical director when you have talent like that coming through the ranks?

After a summer that saw Arsenal part company with several of their own with the sales of Emile Smith Rowe and Eddie Nketiah, Arteta has faced criticism from some supporters for not giving youth its head during his five years in charge. Yet he had been unequivocal before kick-off about the decision to select Lewis-Skelly over Tierney after injuries ruled out first-choice left-backs Riccardo Calafiori and Oleksandr Zinchenko. “There are the circumstances and then the fact the kid has done really well for us,” he said. “He deserves a chance. We are buzzing to see one of our own coming out and playing in a big match like this.”

There had been a clue in the pre-match press conference that Tierney may have to wait for his first Champions League appearance in an Arsenal shirt. Despite insisting that the Scotland defender, who has previously played in this competition for Celtic and on loan at Real Sociedad last season, had earned his opportunity after five months out with a hamstring injury, Arteta also admitted that Tierney is not the kind of full-back who is comfortable stepping into central midfield.

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Lewis-Skelly’s profile on Arsenal’s website describes him as a “dynamic ball-carrying midfielder” and he displayed his creative ability as Arsenal dominated the first half, misplacing only two of the 40 passes he attempted. He was perhaps fortunate not to be shown a yellow card after being nutmegged by Brazilian right-back Vanderson and pulling him back. But it was noticeable that it was Lewis-Skelly rather than Thomas Partey who regularly moved into the central position when Arsenal were in possession, with Jakub Kiwior’s long ball catching Monaco napping for the first of two golden chances spurned by Jesus.

Jesus has only one goal so far this campaign – in the EFL Cup against Preston – and although Arteta dismissed suggestions that he could depart in January as “nonsense”, replacing him would surely be a priority for whoever steps into Edu’s shoes following his surprise defection to join Nottingham Forest owner Evangelos Marinakis’s group of clubs last month. Dan Ashworth is the latest to be linked with the vacant post after his unceremonious departure from Manchester United, albeit it seems largely because of his relationship with the Arsenal managing director Richard Garlick from when they worked at West Brom together more than a decade ago.

Whether Ashworth would be welcomed by Arteta – who is thought to favour his compatriot, the outgoing Real Sociedad sporting director Roberto Olabe for the role – remains to be seen, while PSG’s Luis Campos and Edu’s previous assistant, Jason Ayto, who is filling in as interim sporting director, could also come into the reckoning over the coming months.

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Yet the likelihood is that, even with the injuries mounting up, Arsenal will not be very active in the January transfer window. Ethan Nwaneri, who came on to replace the dazzling Martin Ødegaard once Saka had eased Arsenal’s nerves with a second goal courtesy of the unfortunate Mohammed Salisu’s awful back pass, is also staking his claim for more minutes having impressed in the run to the EFL Cup quarter-finals. He will certainly be needed given the incessant schedule of games to come over Christmas and into the new year.

Lewis-Skelly had long since departed by the time Arsenal scored their third goal after another piece of Saka brilliance. “I’m proud of myself – hopefully it’s the first of many,” the teenager said at the final whistle with Saka watching on like a proud father. “I want to keep learning from Bukayo.”

For the next generation of Arsenal’s academy players, this was compelling evidence that their dreams can still come true.