Every year, there are surprise closers that post 30 saves. There's no sense giving up a great hitter for a closer when you can work real hard on the waiver wire and pick up those sleepers before anyone.
WHat's better, giving up Thome for Gagne, who gets 40 saves (you can't predict 50, that's for sure, even though it's quite possible), or keeping Thome and grabbing 30 saves off the waiver wire?
When you're this weak on RP, you'll have to take a bath to get a good closer. The other teams know you're deperate.
Is someone else out there desperate for steals? You could try to trade Rivas, although I'm not sure what he'd get you.
Like I said, work that waiver wire! That's where I got Gagne last year!