Back in the day, hockey goalies wore 1 or 30 and above, D wore 2-6, F wore 7-mid 20s. Part of the problem now is retired numbers, and the other is that once a player is called up from minors he keeps the number even if he's sent back down. For instance, Chad Ruhwedel owns 5 for the Sabres, and no one else can use it as long as he's under contract, even though he's spent most of his time with the Amerks.