This hasn't really been the case thus far in 2008. Neshek - once on the short list of best setup men in the game - had a few rough outings before losing the season to elbow troubles. Rincon continued (a bteer term might be accelerated) his rapid plunge. Guerrier started out nicely, but he's obviously been extremely overworked, and has been nothing resembling effective for the last month or so. Reyes pitches exclusively to lefties (for good reason, it would seem, as righties have a .422 SLG against him). If only we had another option...
On May 23rd, the Cleveland Indians designated Craig Breslow for assignment. The Twins, deciding they needed another left handed reliever, picked him up off of waivers. In limited work, Craig pitched 11 innings before he gave up his first run. Since then, he's been used mainly in innings-eating roles, or as a lefty specialist if Reyes has already been used. Lately, Gardy's been getting him a little more intensive action, and Breslow's responded nicely. In fact, I'd go so far as to say he's doing the best of any non-Nathan reliever the Twins have right now.
You expect a left handed pitcher to be good against lefties, and Breslow certainly has been.
Craig eats left handed batters. In 66 at bats against him, lefties have fared worse against Breslow than anyone else, including Nathan (they have a lower batting average against Nathan, but a better get on base slightly more often, and have a higher slugging percentage against him).
Now, having a left handed pitcher who knows how to get lefties out isn't anything spectacular, but Breslow's more than held his own against righties, as well.
He's pitched better against right handed batters than anyone except Joe Nathan, and when righties have hit the ball against him, they haven't gotten much on it (one extra base hit in 71 at bats). This is, of course, small sample size, but it's not all that much smaller than anyone else, and he's clearly done better than anyone else. So why is Breslow still toiling in middle relief while Jesse Crain and an overworked (and dangerously near dead armed) Matt Guerrier are given high pressure games? Gardenhire ought to know better than anyone that lefties can get out hitters besides other lefties. Up until late-January, he had the best pitcher in baseball in his employ, and he was a lefty.
In the past 28 days, Breslow has been called in 11 times - and in 6 of those games, he was brought on to face a token lefty or was brought in when there was no other choice. We already have a lefty specialist, and with all due respect to the recently returned 'Everyday Eddie', Breslow has pitched better this year, and it's time that he got a few more late & close game situations to show for it.