Heath Bell: 2007-2011 - 134 saves, 2.53 era
Jose Valverde: 07-11 - 191 saves, 2.91 era
Francisco Cordero 07-11 - 194 saves, 2.97 era
Joakim Soria 07-10 - 132 saves, 2.01 era
Papelbon 07-11 - 184 saves, 2.40 era
Heath Bell 2012: 19 saves, 5.09 era
Jose Valverde 2012: 35 saves, 3.78 era
Francisco Cordero 2012: 2 saves, 7.55 era
Joakim Soria 2011: 28 saves, 4.03 era
All of these pitchers had solid track records of success reaching 4-5 years back with very solid ERA's and saves. And they all completely blew up a year later.
Relief pitchers, especially closers, are a complete crapshoot.