It's one of the most thankless jobs in sports.
Sustaining success on defense in the NFL is extremely difficult, and the defensive coordinator quickly becomes a lightning rod when a team isn't routinely competing for championships. Or even when they are.
The Green Bay Packers are as good an example as any.
Super Bowl-winning defensive coordinator Dom Capers is remembered more for the chorus calling for his long-developing removal at the end of his tenure.
Fritz Shurmur isn't a villain but doesn't perhaps get the full-throated credit he deserves for Green Bay's success in the early 1990s.