It's more due to matchups that he looks so bad. In the first round, there wasn't much he can do against a frontline of Shaq and Amare. He's too small to guard Shaq effectively and too slow to guard Amare. In this round against the Hornets, he doesn't have the atheleticim or quickness to guard West, he may have some effect against Chandler as he's not too much of an offensive player, but he may be too small to go against him for rebounds.

Oberto is a better matchup and more useful against a team like the Jazz, Nuggets, etc who don't have much of an inside presence and big players in the middle.