2 things,
1)If the blazers wanted anything at all to do with Miles, they wouldn't have released him. They had to plan for him getting a contract, so they're on the hook for his cap hit anyways.
2)Greg Oden is coming off of a major injury. Pryzbilla played 45% of the available minutes at the center. He's as good a backup C as there is in the league, and he was the most used center they had last season. Oden is their guy, but they're not letting Pryzbilla walk for a guy they don't want, and a guy they don't want.