I was a Pro Bowler and All-Pro for the Bears, known for my prowess at a position rarely recognized for accolades, yet also made a costly mistake in a crucial playoff game. Who am I?

1. I played in the 1980s.
2. My position group was vital to the 'Monsters of the Midway' era.
3. I was a specialist, not a traditional offensive or defensive player.
4. My error resulted in a critical turnover.