Fernando's case is a strange one. Initially I thought that the biggest issue of this guy has is that he is mentally weak. However, he did quite a lot last year to prove that this is not his biggest issue. Last year, he came here after being frozen out for a whole year. Initially Conte didn't use him. When he used him he scored. And then he was benched again. He never gave up and eventually he was our starter and started scoring normally. Signs of a great player really.
So, what changed this year? The system. I think that his biggest issues is his limited intelligence. This year, we gave Tevez a more free role isolating Llorente a lot in the process. The guy doesn't seem to know how to deal with it. He is used to play with someone really close to him and he can't seem to adapt to a new system. Intelligent players find a way to change their playing style to adapt to any changes (system wise or out of natural causes when they grow older and lose their speed). They alter their playing style in a way that allows them to be efficient. I don't think that Fernando can do this. This is his primary weakness for me. Of course the confidence loss that comes from the lack of goals makes things much more difficult.
I am really sad to say this but unless we intend to go back to our previous system and have someone playing really close to him, the better solution for everyone is for him to be sold. And its a pity cause he can be really good in another system.