I made a point in another thread but will repeat here. I believe Martinez will take the "playmaker" role in the team this season. This is why Onana is key - his job will be to bypass the first pressing wave so that Licha gets the ball in space and can progress it forward. The way Onana positions himself in front of the box also pushes the back line higher, what means Martinez can effectively take central position like deep lying playmaker does. This is a mitigation strategy as we are not getting De Jong type of a player in midfield (also, Mount doesn't seem involved in the build up at all so far, early days but not unexpected I guess).
He's fun to watch that's for sure. I know he was supposed to be good on the ball but the way he passes and sprints to make himself available to receive a pass again is very refreshing to see.