Having 11 starting pitchers on the 40-man isn't a problem. As the tread points out, there's no need to keep them all, and most of them will start the season in AAA. Guys like Worley who will be out of options will cause the Twins to make some tough decisions if they get called up and can't perform. But if they can't perform, and they haven't performed before, exposing them to waivers isn't a bad thing, not for the organization and definitely not for the player.
Worley has a strong enough track record in the NL. He would not pass through waivers. Diamond probably wouldn't either given he is left handed. They both need to be on the 25 man roster next April.
Looking at 2013, it is reasonable to think let them go. However, they both have had success and one or the other is likely to have success again. They both have several years of control left. As the Twins add to the staff this winter it is critical it is guys like Garza that can be seen as a number 2 or young enough like Hughes to have some upside. They need to avoid their usual bargain bin additions. Developing someone in house with service time will have much more value long term.
SSS=small sample size. It's a term from statistics that lets the reader know that the slice of information isn't large enough to extrapolate much meaningful information.