I'll go back as far as I can remember.
Underrated: Frank Warren- DE
just seemed like the LB's got most of the glory back then and rightfully so. But looking back at Warren's career, he definitely contributed over a long period of time. He played 13 seasons for the Saints and I think he's like 4th all-time in QB sacks in franchise history. He played DE in a 3-4 defense just to clarify. You don't really see D-lineman have that kind of longevity anymore with just one team but I guess free agency has changed a lot...
Keith Mitchell- LB. The guy was an undrafted free agent who signed with the Saints around 1997 I want to say. He was a quick LB who was pretty decent at rushing from the outside. I think he was kind of a hybrid LB , especially in Ron Zook's defense. He made the Pro Bowl in 2000 with 6.5 sacks. I remember when he had that interception return for a touchdown vs. Arizona. The QB threw a bullet pass out into the flat that Mitchell kind of stabbed out of the air with one hand and bobbled back to himself for the interception then ran it in uncontested to the endzone
Overrated- already been mentioned.