Before I start, I am not saying we have a rockin' run defense and we are in the top 5 or anything but personally, I think we improved our run defence without even touching the D Line, for three reasons:
1) We have Romeo Crennel. That point alone has improved our run defense just solely because he is a better coach than Clancy. Let's face it, who do you think commands more respect and will have the players trying harder? Do you really think any of the guys cared if Clancy was yelling at them? Try Big Romeo yelling at you and see if you listen. Plus he is simply a better 3-4 coach than Clancy was so we will get better match-ups and play calling. He will be able to make our existing players better. I think he will coach up Studebaker, Belcher and Magee to help the starters. Plus I am sure T-Jack and Dorsey are going to learn a ton from the guy as well as Smith.
2) We improved our spongebob secondary (sorry, I have kids, he is slow and full of holes). By improving the secondary it will allow us more flexibility on the blitz schemes and we won't have to use the LBs to help bail out the safeties. Let's face it the only thing Mike Brown was bringing down last year was the crowd's excitement level. I think now we have a legitimate secondary (no I am not saying we have the No. 1 but we are at least average now). I think simply by not having to worry as much about the pass coverage that we can dial up more and better blitzes and cover the run better.
3) We have improved our offence and special teams. This should keep our defense off the field longer and they won't be gassed in the second half. They should be able to make the whole game now. Let's face it, they spent a lot of time on the field last year.
So no I am not saying we have an awesome run defense right now but I think all things remaining equal we are going to be better than last year and I know there are more changes to come. I have faith in the top brass and I know some more players will be added to help out. So I am not scared...worried maybe but not scared.