Which unit will adapt to the 3-4 the fastest?

Defensive line
Buffalo's defensive front obviously will have one less down lineman, in most cases, than they've had in the past. It immediately shifts more gap responsibility to the three men on the line of scrimmage. The nose tackle is often covering two gaps the most, but both defensive ends will be responsible for handling two gaps as well a fair amount of the time as they grind at the line with opposing offensive linemen.

For Stroud, a 10-year veteran, it's a whole new ball game.

"I've been running a 4-3 all my life and we have a lot of different calls," he said. "It's almost like being a rookie again. We're re-learning all the terminology and all the play calls. It's a work in progress, but I really believe that once we get everything down we'll definitely have a chance. And I think we'll be better than what people are giving us credit for."

The line has its share of veterans in Stroud, Dwan Edwards, who has 3-4 experience, Spencer Johnson and Kyle Williams. The rest of the group however, is largely unproven. With the degree of rotation that most NFL jerseys defensive lines employ in games to keep players fresh, there figures to be a bit of a learning curve. And that's not only for the younger reserves, but the veterans that are adjusting to the new scheme and its responsibilities.

Linebackers
Perhaps no other position group on the defensive side of the ball will experience more change in responsibility than the linebacking corps.

"There's no other way to say it than the differences between the 4-3 and the 3-4 are night and day," said Paul Posluszny jersey. "Just the way we fit up the run, coverages that we'll run. It's completely new compared to what and how we did things the last several years. I would say in all aspects of the game run and pass it's completely different. You have different guys dropping into coverage, different guys have different responsibilities, you have more linebackers on the field. The whole thing is just a new feel."

No one is feeling newer than Buffalo's defensive ends that have been converted to outside linebacker like Chris Ellis and Chris Kelsay. Aaron Maybin is also making the switch, but at 250 pounds he doesn't have quite as much weight to move around in space as his teammates.

"It's a big difference from last year," said Ellis. "We have so many different looks and that's just the base package. So when we get to a point where we can switch things up within the package of plays we already have and give some different looks, it's really going to challenge us as much as opposing offenses. It's a lot to take in, but it gives your defense and our position so many more options because we're asked to cover, stand up, be down, rush. It gives you everything."

Ellis and Kelsay both admit that the toughest transition is the coverage aspect, as they'll be counted on to cover tight ends and backs at times. Both improved as the spring wore on, and they're hopeful their progress continues once they're carrying their pads around as well.

Like the defensive line the linebacking corps has some experienced vets like Andra Davis, Keith Ellison, Kawika Mitchell and Posluszny jersey. But there is a myriad of changes they must master between now and the regular season.