Creighton and Michigan are legit 8 and 4 seeds. Creighton could be the team to give them difficulty. I have found this year that UNC plays better when it has to grind.
When it can play up tempo, its transition defence is brutal, and while they score the other team gets even better looks. Think of games against UNLV this year - even last year against LIU
Creighton will be able to great shots all game long if it keeps at a fairly high tempo.