They probably have the best chance of going through because of how even the group is, but I can see Nigeria getting out of theirs. Don't know much about Bosnia other than Pjanic and Dzeko, but they looked good enough in qualifying.
Colombia will be alright. Jackson, Cuadrado and James are still pretty fucking threatening.
Absolutely 100% agreed. This is why I push for the inclusion of Welbeck so much as well. He's fine with sacrificing himself for the team effort, he's an intelligent runner and passer (provided he hasn't already fucked up! Although his close control is dynamite sometimes), he understands tactical roles and, considering how well he's played centrally when we've sat him deeper on someone like he did against Madrid and Bayern, it's an absolute shame he'll be stuck on the wing the entire time.
I'd even advocate playing Sterling in the middle based on his performances this season, far more so than Rooney. He's an incredible talent.