Lone DM role, particularly for a team playing as ambitiously as we do is one of the positions that's hardest for a very young player to break into imo. Such a complex role requiring a lot of different abilities and requiring a high degree of consistency both on and off the ball.
He could "break through" there for us in two years and still imo be really young for a player in that role.
Players breaking through there at big or fairly big teams as teenagers is almost unheard of. Not entirely, but almost. Busquets comes to mind, think he broke through as a teenager. There are others too not coming to mind right now for me, but the majority break through in that role in their early or even closer to mid twenties - at a high level at least.