To be honest, I kind of am worried. He's poor defensively not because he lacks the technical aspect. He's poor because he lacks effort. Defensemen who are invested into defense are constantly turning their heads looking for plays to shut down or men to mark, have the ability to communicate the system to their teammates so avoid confusion, actively look to take away sticks at all times, etc.
With Hughes, he just stares at the puck unless another player gets in between him and the puck. Rarely do you see the kid look behind him or look to his side to see if there's an open man. It's not about getting the timing down and learning how to control gaps against the fastest players. He's fundamentally not even aware of what's going on around him and that's what makes him horrible defensively.