you mean Gobert? Favors? Hood? if anybody has superstar potential is these guys - not Exum.
Exum has more potential than anyone on the roster. Elite athlete, elite measureables, already good on defense, we saw his shot improve throughout his rookie year, he can get to the rim whenever he wants. Nobody else on the roster touches his potential as an offensive AND defensive player. It just comes down to whether he reaches it or not. I'd put Gobert second on that list. Hood and Lyles on the next tier. Favors and Hayward are what they are at this point. Their potential has been reached, no significant improvements are coming.