The McCargo/Spikes Debate - Who Is To Blame?

In my DT Preview posted earlier today, a little bit of a debate arose in the comments section. Just how effective was the Bills' defense with John McCargo in the lineup, wondered Dock Ellis? Or was Buffalo's shoddy run defense a product of Takeo Spikes, as Kurupt believes?

Ask and ye shall receive, Bills fans. I crunched the Run D's numbers, separating the stats out into three areas: "The Defense With McCargo (and without Spikes)"; "The Defense Without McCargo (and with Spikes)"; and "The Defense Without McCargo, With Spikes and Not Considering Incredible Rushing Offenses". (Sorry for the long titles - my creativity is at a minimum this evening.) Here's how it breaks down:

Note: The Bills faced three teams (San Diego, Jacksonville and Tennessee) that had top-5 rushing offenses in 2006. McCargo did not play in any of those three games.

What to Make of This?
Let the debate rage on. In the 11 games when Spikes played and McCargo didn't, the Bills gave up nearly a full yard more per carry and 40 more yards per game. Even when you factor out those 3 games against Top-5 rushing teams, there's still 20 more yards per game and half a yard per carry. It's painfully obvious that the run defense broke down horribly after Week 5 - but who is to blame?

This stat, to me, tells the tale: in just four games last season, the Bills held their opponent to under 100 rushing yards in an entire game. Three of those games occurred in the first set of 5 games (at Miami and at home against the Jets and Vikings). The other was Week 7 against the Patriots. Spikes played that entire contest, which was a surprisingly solid defensive effort given the 28-6 lopsided final score.

My take: This has more to do with McCargo than it does with Spikes. I'm not trying to downplay Takeo's disgustingly bad play by any means - he was part of a run defense that was just terrible last season. But I'm going to stick by my theory that McCargo's presence helped. He didn't play much until the Jets, Vikings and first half of the Bears games. The first two were two of the four contests that the Bills held their opponents under 100 yards. And by all accounts, McCargo had been improving quickly and earning more playing time up until the point he got injured. If he's healthy, his presence alone should statistically boost our run defense. (Notice I didn't say fix.)

But that's just me. Can't wait to see some of the comments on this one.