All the people saying "even if Graves slows down, he'll still be near the top of the league in saves" well that's irrelevent unless you use retroactive stats. Lets say you hypothetically know that Graves will finish with 5 more saves than Gagne, as well as their ERA/WHIP/K's will be identical from here on out. Who would you rather have for the rest of the year? Graves at 55 or Gagne at 50? Gagne at 50, obviously. Because 20 of Graves' saves are already accounted for, while 10 of Gagne's are accounted for.
Do you really think Graves will continue at this pace? If you do, you're crazy/ He's not pitching as well as most think - guys like Baez, Kolb, and Dotel have been pitching better. They just havn't had the save opps yet. If you can get better than draft day value for Graves (obviously you can find somebody who thinks the 20 saves Graves already has will benefit him somehow) then by all means do it. Graves has been decent, and doesn't even get a lot of K's (not that K's matter so much for closers). I'd rather have Baez from here on out.
My advice: get what you can for Graves now. Did anybody think highly of him before the season? Not really. Is he doing better (other than save totals, which are random) than expected? Nope. So why is his value so high? Because of some lucky save opps? Everybody knows about "buy low, sell high" but they get cold feet when they feel like they have a stud closer on their hands.
And for the guy that asked about Sheff: hell yeah, I'd do that in a second. The possibility of surgery makes me worry but if you want big rewards you have to take big risks. (The risk being Sheff's health, not Graves' success. I'm pretty sure Graves has had his 15 minutes for this year.)
"Jack, will you call me, if you're able?"
"I've got your phone number written, in the back of my Bible."