Vick says he "didn't know" there was dog fighting on his property.
Take a look at this picture of his property. Note the kennels on the left, and the larger enclosures on the right.
We know he's been there, because he said he "rarely" visited it (which we can safely say is probably more then once). These kennels and enclosures are right next to the house. So, if he's been there even "rarely", he would have to have seen it. What did he think his cousin was doing, running an animal shelter? Considering he was the proud owner of "Vick's K9 Kennels", don't you think he'd be at least curious about what his cousin was doing with all these dogs?
Here's a cache of his web site touting his commitment not to "raise dogs for fighting" and all the careful screening he did.
And, yet, right there on property he owns and presumably pays taxes on, his cousin has 50 or 60 dogs in kennels. And not a chihuahua among them.
Good luck with that defense. Even without the two people who seem to be cooperating with federal authorities, I think he's going to have a tough time selling that story.