Originally Posted by Numinous
I'm following SirBenoit's bet and say it's Vegapunk, it's the only person in my opinion that makes sense being introduced now.
I agree as well.
For Vegapunk it would make sense to wear a lab coat. At least he was depicted as wearing one here
The coat we get to see here could very well be one.
Admittedly, the shoes look similar to Aokiji's. But they could also just be a sign of affiliation to the marines... alternatively, they'd also fit to depict a doctor/surgeon I guess (which would fit to Vegapunk as well).
The way in which the unknown person is addressing Law makes it seem like he was Law's elder. It would fit Vegapunk, who was said to be an "old geezer". (Although this doesn't apply exclusively to Vegapunk.)
Still, I'd rather rule out Aokiji here, because when looking at this page
, it looks like Law is in pain and even blood is coming out of his mouth (?).
Thinking of Aokiji, he'd probably just frozen him in some way to incapacitate him for some decent smalltalk. This looks more like some sort of poison or something... which wouldn't really be Aokiji's style IMO.