Perhaps Trek is interested in a podium but why would Nibali want it? I mean he's 36, he's got a gazillion GTs in his career, his legacy won't change if he blows up and finish this Giro 15th (which is rather unlikely anyway, considering the riders behind him).The realistic goal should be a podium.
I'm pretty sure in 10 years we'll remember his performance in this Giro a lot more fondly if he goes into a suicidal attack from Bondone or Agnello rather than him waiting for TGH or Almeida to pop and find himself on the podium without ever attacking once.