The current Toronto Maple Leafs roster is built around four players they drafted and developed into superstars (Morgan Rielly, William Nylander, Mitch Marner and Auston Matthews), and outside of a few other pieces, the vast majority of the rest of the roster is made up from Toronto Marlies graduates.
William Nylander, Pierre Engvall, Frederik Gauthier, Kasperi Kapanen, Andreas Johnson, Trevor Moore, Travis Dermott, Justin Holl, Martin Marincin, Dymtro Timashov, Mason Marchment, Adam Brooks, Pontus Aberg, Michael Hutchinson, Kasmir Kaskisuo and Rasmus Sandin are players who’ve played with both the Leafs and Marlies.
It’s most of the roster.