Here is the list of current NL-closers and their current salaries in my 4X4 NL-only 12-team keeper league with the ones who were drafted in bold.
NYM Billy Wagner $37
PHI Tom Gordon $30
ATL Jorge Sosa $1/ Ken Ray $10
FLA Joe Borowski $21
WAS Chad Cordero $15
STL Jason Isringhausen $35
CIN Eddie Guardado $33 (FAAB)
MLW Dereck Turnbow $2
HOU Brad Lidge $9
PIT Mike Gonzalez $11
CHC Ryan Dempster $1
SD Trevor Hoffman $21
LA Takishi Saito $10
SF Armando Benitez $20
COL Brian Funetes $2
AZ Jorge Julio $10
The ratio is slightly better than my AL-only but not by much. Five of the 16 current ML closers were taken at the draft.
Amongst the non-drafted closers are two failed starters, Ryan Dempster and Jorge Sosa, and three free agents taken from the pool this year - Takashi Saito, Ken Ray and Jorge Julio.
(FWIW, all three were taken by me with possible closer roles in mind. I waived both Saito and Ray to activate other players from my reserve. Saito then re-acquired the role following Gagne's injury, and Ray was given it following Reitsma's injury. And further FWIW, I drafted Jorge Sosa in 2005 with the failed starter theory in mind but dealt him after his successful 2005 starter campaign.
If you want a clue to the third closer-in-waiting I may cut - Randy Messenger with the Marlins. Ed: A two paragraph parenthetical?)
That leaves almost half the current NL closers as players drafted as middle relievers who graduated to the role. (Eddie Guardado likely slots with the free agent ones as he was technically in that pool prior to the FAAB process.)
Looking for middle relievers to fill out bail trades seems to offer a good chance of acquiring a future closer, no?