Royals manager Buddy Bell said he doesn't see his team carrying Zack Greinke or Brian Bannister as relievers if they don't win rotation spots.

That's pretty much what was suspected. There's only likely to be room for one of the two in the rotation, and Bannister should be viewed as the favorite going in. In order for both to make it, Jorge De La Rosa would have to struggle this spring.
From Rotoworld.com

Once thought of as a must have prospect and future ace has litterally fell off the planet and looks to be headed to AAA to start the year. I think this might be a decent gamble for Krivsky. Send Milton and Belisle/prospect to KC for him. Grienke is still young and definatly has upside. There rotation looks like Meche, Perez, Elerton, Hudson, & De La Rosa/Bannister. Some of the non-roster invitees that may have a chance could be Duckworth, Day, or Brazelton.

Now I believe the Reds have yet to recieve anything in return for LaRue and Cash that was sent to the Royals at the start of the off-season. Maybe we could use that as well to obtain Grienke. This could be one of those small risks.. high rewards deals that Krivsky seems to make.