They seem to be underestimating Niang big time. They think Brogdon can shut him down all alone like he has past shooting forwards they've played in the ACC.
Not saying ISU is going to win, but you don't shut down Niang with only one player, no matter how good of a defender he is. You scheme to get the ball out of his hands/deny him the entry pass in the low post. If he catches it in good position you've already lost. If you double him at this point he finds the open man, if you leave him one on one he scores.
Or you run at him on defense to get him fouls so he has to sit on the bench. Pretty much the only way to stop him is to get the ball out of his hands or get him out of the game.
If I were UVa I'd focus on stopping ou other players (Thomas, Nader, Morris), because Niang probably won't be stopped, but can't carry the team on his own. If The trio of Niang, Morris, and Thomas keep playing like they have ISU will be an extremely tough out.