This sort of extends from cmath's featured post about how the Twins are underestimated by the mainstream media/fans. Only, I want to focus on one aspect: The Bullpen. How it's changing, and how it can effect a game. Especially for the Twins.
The Twins bullpen has outperformed it's talent for about 5 years now. Even before Nathan, Crain, etc. Gardy, Andy, and TR are all together with the focus on the bullpen. I think it's safe to say that Eddie and Hawkins pitched above themselves in '02 and '03. Remember Tony Fiore? You can even argue that Romero's success was a result of the way the Twins handle their pen. Same with Reyes last year.
The bullpen is becoming more and more important to a team's success every year. I think it's not long until you see 12-13 man bullpens become the norm. Middle relievers and long men are even more valuable then teams now consider them, IMO. The SABR philosophy even considers your first reliever the most important to your success. In today's game, your bullpen also effects the game more then any 1 starting pitcher because your bullpen pitches in nearly every single game.
Consider the Twins in their current position. With 3 potentially shaky starters, it would greatly benefit the Twins if they could have another Guerrier-ish arm. Almost as much as a different starter. You could get to the point where you only have to ask for 5 innings from the back end of your rotation because you'd have spot starters ready to plug holes at any time. -And you wouldn't have to burn your late inning arms early.
You figure that you're going to get 4 innings a week from each of your 2 long relievers. You can have them extend 5 inning starts to your set up men without much of a drop off. Especially when you consider guys like Silva, Ortiz, and Ponson are the starters.
Basically, my opinion is that you can get away with a sub-par back end of the rotation if you have a second reliable long reliever. -And it's easier to get a reliable long reliever then a reliable starter. For the Twins, at least.
With the current state of 5-man rotations and climbing payrolls, I think the long relief role will become more and more important for teams that cannot afford to buy solid starting pitchers. 2 solid long relievers + 2 iffy starters will cost your team less then 2 proven starters + 1 throw-away long man.