It would be a good debate to decide who is more specialized: a closer or a DH?
On the one hand, a closer does all the things a pitcher does, just infrequently and briefly.
On the other hand, a DH basically only does one thing: hits.
The role of bullpen pitchers have become more and more specialized with closers basically restricted to the 9th inning and teams attempting to more and more compartmentalize their 8th and 7th inning pitchers.
Last season, there were 15 pitchers with at least 30 saves. None threw more innings than Fernando Rodney.