I sincerely believe Judd has it in him to be in the top 1-2 players in the league. He has the tools to be anything he wants to be- he's big and will only get bigger, has absolute lightning pace, great skills, and the beginnings of a very acute football brain.
Having said that, geez. Its his second year, he's 19 years old. Put simply for most football players there first two years on an AFL list are about development, and anything you get out of them on field is a bonus. Judd has been the best sort of rookie this year and last in that he was contributing as well as developing, but in reality, what Judd can do this year is not half as important as what Judd can do in three or four years time. Development is still the number one priority.
The fact that he has already put some runs on the board just means the expectations have been ratcheted up a little. I'm not sure I'd say he's going through second year blues- perhaps he's having a little trouble coming to terms with being a marked man who everyone wants to tag- iirc, Cousins had similar issues during his emergence.
Realistically, don't expect *anything* from Judd at this stage. Its lovely that he is capable of getting 20 touches a game during his development phase, and putting in the occasional game breaking performance. When he takes the next step, he'll be a superstar, but for the moment, just trust.