One of the criticisms of the Twins is that there rotation going to consist of five guys who are bottom of the rotation starters. The Twins success depends on the three starters with the potential to be better than that. Mike Pelfrey, Scott Diamond and Vance Worley all need to be above average big league starters. The Twins have a number of candidates to share the fourth and fifth spots in the rotation with Kevin Correia. But they don't have anyone else ready for the big leagues who has the ability to be a top of the rotation starter this year.
Pelfrey is the veteran of the three. He put up close to 200 innings for four years until last season when he had Tommy John surgery after three successful starts. It usually takes more than a year for a pitcher to recover from that procedure, but Pelfry has appeared to be healthy all spring. If he is healthy and effective he can be a top of the rotation starter.
Diamond was a pleasant surprise for the Twins last year. He was taken in the rule 5 draft for the 2011 season and spent the entire year at AAA. He started last year dominating at AAA and became the Twins best pitcher once called up. If he can repeat last year's performance over a full season, he will give the Twins a solid above average starter with 200+ innings.
Worley, who came to the Twins in exchange for Ben Revere, is a year younger than Diamond. He had a good 2011 season after being called up from AAA and then struggled in 2012. Some of that may be attributable to bone chips that were removed last fall. If he pitches for a full season the way he did in 2011, he will give the Twins another solid number two starter.
The Twins pitching is unlikely to be a strength. None of these guys are going to consistently dominate other teams. But with the offensive potential of their lineup, they don't need to for the Twins to win. They just need to pitch well enough to keep the Twins in games without overworking the bullpen. A key to the Twins being competitive is for these guys to give the team quality starts most of the time.