For the moment the battle for podium seems to be between 5 guys.
O'Connor was riding like a madman today, and his Giro last year seems to indicate that he's very good in the third week. He probably has the weakest time trial of the 5, but he did defend himself relatively well in the first ITT of this Tour. With his 3 minutes advantage on the other contenders, he's my favorite to take 2nd place.
Carapaz is the obvious choice as he's on paper the strongest of the contenders and also tends to improve as a GT goes on. However, I don't think he has looked as sharp as one could have expected this Tour and he has already spend a lot of energy. He also doesn't have the strongest time trial - even though he did decently in the first one - and I just have a feeling that he isn't quite where he wants to be.
Uran has looked solid and has a good ITT, but in recent years he's had a tendency to fade in the third week. He's also not very agressive and will have to rely on his time trial, which I don't think will be enough to grab a podium spot.
Vingegaard is in unknown territory but has looked solid, even though he was in slight trouble yesterday. He has the strongest ITT of the 5, but will it be enough? I have a feeling that it won't.
Mas has looked sharper than ever in the beginning of a GT and always improves a lot towards the third week. His ITT was disappointing but I expect him to be a lot better in the second time trial. He also looked good yesterday despite crashing earlier on the stage. Overall, I think he looks better than ever and he's my pick for the last podium spot.
Of course a lot can still happen, but for now at least it looks like a fight between those 5.