Here are five players in the Twins system who I think are currently undervalued by fans. They are in a word "disappointments" because they have not had the immediate success of future stars. I am not sure any of them will ever be stars. But that is really the wrong measure of any prospect. Stardom is something that you can hope for, but most prospects are going to end up with flaws that prevent that kind of success. The real question is can they be productive major league players.
Trevor Plouffe is top on the list because he is closest to being ready. His status is similar to Denard Span's a couple years ago when the Twins traded for Carlos Gomez. This time the Twins went out to Japan for Tsuyoshi Nishioka to be Alexi Casillas double play partner. Plouffe lacks outstanding defense, but he is a legitimate major league shortstop. What I think many people miss is that he can be expected to develop a fair amount of power. Not the juiced power of Rodriguez/Tejada etc, but the kind of power you used to be impressed by at shortstop. He is going to end up an offense-oriented shortstop who regularly hits 20 home runs each season.
Chris Parmelee is another first round pick (there is a pattern here). Again he has developed too slowly for impatient fans. But he projects to develop into a major league power hitter. He can play a corner outfield spot, but will probably end up at first base. He isn't going to turn into the next Justin Morneau, but he may be a solid offensive bat in the middle of the lineup.
Deolis Guerra came over with a lot of hype in the Santana trade. He hasn't lived up to it. But he is still very young for his level and very talented. With patience he may end up being that ace Twins fans have longed for since Santana left. But he is at least a year way from the major leagues.
Carlos Guttierez is underrated largely because he projects as a bullpen pitcher. But his sinking fastball could make him a reliable closer who can not only shut down another team, but can come in with guys on base and get a ground ball. He has the potential to be the next pitcher in the Reardon, Aguilera, Nathan legacy of top Twins closers.
Bobby Lanigan is a stretch (I needed a fifth underrated prospect). Lanigan has had some struggles and injuries but he is still a big strong kid with the potential to be a major league starter if he can stay healthy.