I'm in 14 team keeper league. and believe it or not, I kept him as a "keeper" last year. I just dumped his ass to the waiver wire. He could just be slumping right now of course, but what's the purpose of keeping him around? I probably wasted a keeper on him last year, but I really thought he'd be incredible this year.
Simple, I think. If you have a team that looks as though it will contend, you definitely trade him to a bad team that needs to build for next year, or just drop him.
If, however, your team is unlikely to contend for a money position, then he's worth holding, assuming this to be a an auction league where you got him for a buck. Otherwise, it's a big adios.
I don't think that Wagner is even next in line as closer for this year if Graves does in fact get traded (unlikely IMO). Wagner is not pitching well now and has a better chance of getting saves in AAA than in the majors for this year. Next year however could be a different story. This guy has huge potential, so unless there is any closer still out there, I guess you might as well stash him on your bench.