There are two kinds of people in the world...
A) If you believe that the universe conspires against you, then your closer is destined to injury unless you also have his setup man. Having this man, who could step into the closer role, prevents injury to the current closer.
B) If you are sane and rational, then having the closer and setup man from the same real-life team is simply a reasonable insurance policy.
Without revealing which type of person the Zingrods' owner is, the Zingrods have Hoffman, so they picked up Wall in the 2000 preseason draft.
Update 5-29-2000: Reeling from injuries and badly needing help from the free agent pool, the Zingrods released Wall to make room for new acquisitions. Hopefully the plethora of alternate closer options in the Zingrods' bullpen will be enough to keep Hoffman healthy.