Tbh, I'm not really as optimistic as most people here. Sure, the way the stage was ridden really didn't suit him, Trek tried to make it more of a long effort but didn't have the strength to do so, so the stage ended the way that suits Nibali the least, in a steep uphill sprint.
So yeah, here you have your excuse, but the reality is, even Nibali doesn't finish this stage this badly if his shape is good. As strange as it sounds, I wouldn't be as worried about this if he had worse shape on the Etna as I would see it as a sign his shape just has to gradually improve throughout the Giro. But he didn't. If anything it looks as if he has gotten worse since stage 3 and even then my thought was he has to improve to win the Giro. After today I'm seriously doubting if he can do that.
We will see. I still see Nibali as the favorite for the win, especially as Kruijswijk, the guy I would usually consider the biggest danger for him looked even worse today, but the situation isn't perfect. Seriously if the big danger everyone is talking about wasn't Wilco freakin Kelderman, I probably wouldn't have Nibali as the favorite anymore.