The problem with our defense started before the season even started.
Remember we went into the season with only 23 defenders on the roster. That is a very small amount by usual NFL standards. Meaning when someone got injured we didnt have a usual rotation in place. We didn't have a solid rotation to keep guys legs under them the whole game or season. Combine that with older defenders who lost their legs towards the end of the year especially since we didn't have enough players for a solid rotation to rest them. Older players such as Okeafer, Haggans, Berry, Robinson, slightly Wilson. Players such as Cody Brown and Will Davis getting injured expanded on this issue.
I know some my not believe this but losing MAtt Ware was a bigger issue then some may have realized. He wasn't flashy but at least he was usually where he was supposed to be in the zone coverages called, he rarely got faked out by a play action or pump fake. And Rashad Johnson not coming along as fast as we thought he would didn't help matters.
Hate to say it but letting go of Hood was a mistake. I know his 08 season wasn't all that great, and was making not overly expensive but decent money but letting him go was without a doubt a mistake especially in favor of the 5-7 shorty Adams, the old Ralph Brown, and the uber raw Toller. Compounding this was the fact that Ware was injured and Hood played very well for the Titans this year. I don't think we do this often over the last 3 or so years but we without a doubt went the cheap route on that one.
Finally, Davis wasn't Wiz first choice. Butler from Pitt was his first choice. When Butler said no I think Wiz went with what he knew in Davis rather then shake the boat. I think he went the safe route.