Capers has run some hellacious defenses. His Pittsburgh defenses ranked 12th-3rd-3rd. Points allowed ranked 2nd-8th-2nd. The year before he and Cowher got there, they ranked 22nd overall and 23rd in points.
The Jacksonville D ranked 25th the year before he got there. The ranked 5th his first year (1st in points allowed) and 9th the second.
As head coach in Carolina, his defenses ranked high right out of the box. They began 8th and 2nd in points. Then they plummetted. In Houston, they've been at the bottom consistently.
But you look at when he's been DC, and it's consistently at the top. I think he's definitely a career non-head coach (in the NFL) from here on out.
I also found another connection to Nick Saban.
Dom Capers began his coaching career at Nick Saban's alma mater, Kent State, as a graduate assistant. He coached there from 1972-1974. Nick was a defensive back on that '72 team. In 1973, Saban also became a graduate assistant at Kent State. So they coached there together during the '73 and '74 seasons.