I think that Pettersson and Hughes were pretty good before coming to the NHL. I am lukewarm on Green, but i am not going to give him credit for 'developing' those two, they are future superstars who were basically instant 'just add water' performers. I seem to recall Green scratching Hughes early on, so I think it was more of a 'show me what you got' and it was understood pretty quickly that you don't scratch Hughes.
Maybe you could make an argument for Boeser, but even then, he had a monster season right out of the gate.
If there's a coach that developed anyone on this team, it's the goalie coach Ian Clark. What he did with Markstrom outclasses anything Green has done.