Not that I really have a bunch of sources, but I do happen to be acquainted with someone "in the biz". This person recently relayed to me a couple of interesting tidbids.
1) Kerry Wood wants to be the closer and has expressed as much to the coaching staff/manager and the front office. It's management (on-field and front office) that want him to continue to start.
2) Mark Prior's right shoulder is bothering him.
Before anyone flies off the handle and states that I'm making this up. Let me just say that everyone can choose to believe this or not. The person who told me these items truly believes they are fact and really is "in the business" with contacts within the Cubs organization.
Here's to the hope that at least one of these is wrong. Lord help the Cubs if Prior isn't fully healthy all season.