For most playoff leagues, the easiest and most common format is a points based system where, for example, a point is worth one point, a rebound worth two, a three pointer worth two, an assist worth two and a half and a steal or block worth four. Or something like that. For the sake of simplicity, we're going to assume that there are no averaging metrics or categories like field goal percentage, free throw percentage, etc.
We're going to further assume that players cannot be added, dropped or traded during the course of the playoffs. So there are but two components to a player's value: (1) how many fantasy points per game he's good for, and (2) how many games his team is likely to play. To the extent that a team is expected to play a lot of games, players on that team will have more opportunities to put up fantasy points.