I agree that Messi will drag Argentina to at least the quarter finals if not furtherThere's been a lot of predictions about Argentina crashing out of the group-stage. I dunno if that'll happen.
Croatia doesn't have much up-front in terms of offensive play and their midfield is woeful without Modric.
Nigeria is a young team that is still working out kinks a week-out from tournament. Our defence is also not ready for the World Cup, even if they're facing Higuain ()
I can't say much about Iceland.
I think Messi will put Argentina on his shoulders and they'll make it out.
bbut Croatia's midfield and attack is scary on paper (Mandzuckic, Modric, Pjaca, Rakitic, Kovacic) but they will likely let in lots of goals