I can understand why Slingblade might think that....Even though I disagree.
Porter is on a team where it is possible he will be the fourt or fifth option...
Now he might pass Brown on the depth chart like every mag is predicting, but it's also possible that he won't, and they will keep him in the slot. His TD numbers might go up, but I think it's more likely that they will stay right where they are.
Once Timmy and Jerry are gone, next year most likely, Porter will be the guy, and his numbers will rise dramatically...
But calling him a one-year wonder, sounds like someone only watched the Raiders when they were dismantling his team.