I haven't done any analysis, and am just looking at some raw stats, but I thought you all may find these interesting:
The year(s) Gerg was presiding as dc are denoted with a "g" following the ranking.
New York Jets Defense Ranking by yds/g:
1994: 22 g
Broncos "" :
1995: 15 g
1996: 4 g
1997: 5 g
1998: 11 g
1999: 7 g
2000: 24 g
2001: 23 g
2002: 32 g
2003: 29 g
Now I know the quality of the offense has a lot to do with how many yds/g the defense gives up. That being said, these stats make me think Gerg is a mediocre DC at best. Both the NYJ and KC were worse with him, while the Broncos were somewhat better.
I don't really know where I'm going with this, other than I'm trying to reason a way into believing our defense will be serviceable next year. I'll be extremely pleased if Gerg can just get our defense to mediocrity, as I believe RR can handle the rest on the other side of the ball. We could see similar stats to that of denver from 1995-2000 in that case, because (I haven't looked) Denver had a solid offense during that time.
Anyway, sorry if I wasted your time. The stats can be found at : www.nfl.com/stats