I think a lot of people concentrate too much on one-on-one matchups, and forget the other aspects of center defense. Yes, Krstic is a poor matchup against LA and Orlando, due to their size and skill at the center position.
However, I also think he's a bad matchup against Chicago; he can't keep up with Noah's speed, and he'd get killed on the boards. Against Miami, I worry about Krstic's poor rotations and his inability to cut off penetration. Even teams without elite centers can exploit Krstic's softness and poor defense / defensive rebounding.
Krstic played pretty well last night, but I want his minutes in the playoffs to be limited. We'll be fine so long as Shaq and JO manage 35 combined minutes per night. When we start talking about Krstic (or BBD) filling in much more than that, I get worried.
We need Shaq.