AK47 already mentioned Pat Neshek, and while I would love to push a friend of the blog forward, I have to think the Twins front office will want to go with someone who isn't coming off TJ. This is a good opportunity for Neshek, though. If he pitches well, he may see some time in the 8th inning. Other than Neshek, the three most logical options for the Twins closer role are Matt Guerrier, Jon The Giant Rauch, and Jose Mijares. I'll review all three, starting with Guerrier.
On the surface, Matt Guerrier had a great year last year, posting a 2.36 ERA over 76.1 IP, striking out 47 and walking only 16. That's a K/9 of 5.54 and a BB/9 of 1.89. However, Guerrier pitched to a 4.35 FIP and a .222 BABIP, while his LD, GB and FB% stayed roughly in line with his career averages. His FIP was a 2 full runs higher than his ERA. This is not good.
Additionally, Guerrier's excellent walk rate in 2009 was out of line with his career BB rate of 2.81. This, as well as the ERA/FIP split and the extremely low BABIP, is why we see both Marcel and CHONE calling for a regression in Guerrier's 2010 performance. CHONE is is predicting 71 IP, 4.18 ERA, 6.12 K/9, 2.92 BB/9, as well as a FIP of 4.49. Marcel is seeing roughly the same thing: 71 IP, 3.93 ERA, 6.46 K/9, 3.04 BB/9 and a FIP of 4.74. Essentially, CHONE and Marcel are calling for a regression to the career norm of Guerrier's walk rate, and a normalization of his BABIP that bring his ERA in line with his FIP.
This is Matt Guerrier in a nutshell. If the Twins use him and CHONE and Marcel are right, then we'll probably hear a lot of commentators talk about how Guerrier just isn't "suited" for the 9th inning, or can't "handle the pressure" of the closer role. The reality may be different: 2009 was great but probably the result of a bit of luck. There's nothing wrong per se with a closer with an ERA in the 4s and a low K rate, but I have to imagine Twins fans are wanting something more. We'll see soon whether Rauch or Mijares give reasons for optimism.