That's an awesome explanation.
Years ago I saw a game in Atlanta and the Braves brought on a guy called Smoltz who was apparently superfast, right at the end. Didn't realise he was a closer.
Never heard of "spot relievers" either.
So, I'm guessing starters are more valuable that relivers? Which is why the salaries are so different?
http://espn.go.com/mlb/team/roster/_/name/nyy/new-york-yankeesSome of those salaries beggar belief.