The prevailing opinion among NBA fans is that the NBA's Western Conference is heads and tails above the Eastern Conference in terms of talent. That is true for the most part, but there are some teams in the Eastern Conference that definitely stand a chance, the Miami Heat being the top team.
Some other teams need help to get closer to the top teams or to help them make the playoffs. That help in some situations will be coming from some of the teams "big men".
Every one of these players plays at the center position, and the teams they play for need them to take the next step in their careers, or in two cases, play well as a rookie.