i liked Oliver and his big play ability, but his part in Olivadotti's copiously porous defense precludes him from being on my list. Sure he might intercept 5 passes a year, but how many times did we see him have James Lofton or Al Toon run past him, or see Rob Moore make a big play in his face.
Also, being a pro-bowler should eliminate someone from "most underrated" contest, although it is possible for a pro-bowler to be generally underrated of course (ie. Fryar and Timbo)
just some names that pop into my head:
1. McDuffie
2. Parmalee
3. Gardener
4. Jeff Cross (did make the probowl in '90 though, but was a 9th rounder)
5. Kirby