This is going to be short because the rotation battle is pretty clearly defined:
Certain barring injury:
All but certain:
Until he shows he is healthy and able to pitch, last years injury leaves some questions. No one expects that to be a problem, but he has said he still has some pain and that is never a good sign.
Everyone wants Liriano to take this spot by demonstrating he is back to his 2006 form. The other two primary candidates are Perkins and Duensing and neither one can compete with a 2006 Liriano. Assuming Liriano is something more than last ear but less than 2006, Perkins is probably next in line based on experience. But the more Gardy talks, the less I think he is really ready to put last year behind him. Duensing pitched well in the rotation last year. But its not clear if he can do that over a full season. The other two candidates, Swarzak and Manship, are longshots. Swarzak got the rotation call before Duensing last year, so a good spring training and continued struggles by the lefties could put him in contention. Manship is probably more showcasing himself for an early callup, but if the others all stumble he is a very longshot if he steps up his game.
Sixth Spot: Obviously this is one of the losers in the group above. But it is important to remember that getting through the season with five starters would be very unusual. Whether the Twins hang onto Perkins may depend on whether one of the other pitchers is clearly ready to step in. If there is stiff competition for the fifth spot in the rotation, then Perkins may be gone. But if the 5th spot is filled by default, they may hang onto Perkins as the only guy who has shown he can pitch successfully in the major leagues, even if he isn't their first choice. That is also true, if Liriano takes the job, but Duensing and Swarzak struggle.