He's played in the bullpen, and wasn't very good. He was terrible as a starter, and maybe only slightly better in the bullpen. His fastball velocity from 2006 was consistently around the mid-to-upper nineties, while his wicked slider would reach around 90-91 consistently. Absolutely deadly pitches, not to mention his curve was in the mid-to-upper 80's as well. He was throwing gas, with wicked rotations, stuff that was pretty much unhittable. He was the best pitcher in baseball, by far, in his portion of the 2006 season, and now he's a guy who can barely make it through three or four innings.
I don't think moving Nathan is a good idea, especially considering what we have to replace him with. Sure, he has value, but we have no one to close games. We would have Pat Neshek, but I'm not sure what ever happened to him. I know he had a serious injury, but if he ever comes back, he'd certainly be a question mark. We don't have the bullpen depth that we had even two years ago.