It's hard to tell right now. Saad will get his cup of coffee, and probably go back to juniors. When he has a full season and has ROTY votes, then he may be comparable. But the fact is this, Saad is a good young player on a great Hawks team. Castro is a great player on a team that's in shambles.
It would be a better comparison if Saad was around during the ABC years.
I think too many fans have the cart before the horse when it comes to Saad. He had a very good camp, and proved his worth briefly in playing with the big boys. If he begins showing up in stats column, and his line becomes extremely effective, your argument becomes very valid.