Before I get down in the weeds, I want to say that this is a great signing. It's great that we're bringing in some serious talent via free Agency. It's great that the Bills are willing to spend money. It's great that they brought in someone who will make current and prospective players believe in the Bills. But remember: We very likely paid Mario Williams more than any other team was willing to pay him. That's true with pretty much every free agent any team acquires. With that, some thoughts on Mario:

• Don't expect Mario to turns the Bills into a 12-4 team. One player rarely makes more than a one-win difference. The Bills need a very good LT out of the draft, a healthy Kyle Williams, superb seasons out of Aaron Williams and Drayton Florence, and a showing from their 2011 and 2012 draft classes. I also think the Bills probably need another 1-2 free agent signings to will in depth at WR and along the offensive line. KC Joyner made the point that defenses will attack your weakest link. There's no point in having an incredible left-half of the line if the right-half is porous.
• Mario is unlikely to be a locker-room leader. And that's okay. He was known for being quiet in Houston and he'll be quiet here too. Kyle Williams, Marcell Dareus, Nick Barnett, Drayton Florence, and George Wilson are all bona fide defensive leaders.
• He'll be lining up at left defensive end. Or so said Nix on WGR and apparently this was one of Mario's requests. I'd imagine he'll get moved around a lot: LDE, RDE, DT, OLB. Still, I'm not a fan of the quarterback being able to see what's coming.
• Kelsay will be a lot better. I've never been a Kelsay hater, especially not when he's got his hand on the ground. You have to love Kelsay with double-teams going everywhere but his way and the guy gets to line up on the right side. I think a lot of folks will be clamoring for Carrington, but I'd bet Kelsay has the inside track on the starting job.
• This means the Bills are running a traditional 4-3. The good news is that our defensive line is perfectly configured to run this. The bad news is that our linebackers are not. Merriman's a poor fit for the scheme. (Great article on systems here and here.)Sheppard has a lot more responsibility in the middle. And Barnett moves into the Will LB position. I suppose Merriman gets plugged in at the Sam LB. If all this is true, you wonder how guys like Moats, Eddins, and Morrison fit in. My gut says Morrison looks damn good in this system, Eddins is too young for us to care, and Moats is on the outside looking in. I'd love to see Bryan Scott resigned for depth.
• Teams will look for other ways to victimize us. We're still a little light up the middle. Kyle Williams always did play bigger than his size, but he's not a prototypical over-center DT and neither is Dareus. Our inability to stop quick slant passes remains and teams will look increasingly to the quick plays.