There are a lot of questions of which players will fit where, how much will the 3-4 be truly used, and what expectations can be assumed of a new system on a group of players that as a whole do not fit into the scheme.
The 3-4 defense being installed by Dom Campers, Kevin Greene, and Winson Moss is based upon the athleticism of its linebackers and the stoutness of is three-down lineman.
If executed correctly, the Capers' 3-4 looks similar to what is seen by the Pittsburgh Steelers rather than the Mike Nolan/Rex Ryan Baltimore Ravens 3-4 in which the weak inside linebacker must consistently take on an interior lineman so that the edge rushers and strong inside linebacker can attack the running game and passer at the line of scrimmage or the backfield.
It is expected in Capers' defense for the down linemen to not only engage and mirror the offensive line, but also force double-teams and be strong at the point of the attack for running plays.
Johnny Jolly, Cullen Jenkins, Justin Harrell, Ryan Pickett, and 2009 first-rounder B.J. Raji are all going to see considerable time as three-down linemen. Pickett, Raji, and Harrell could be rotated early and often in the season at the nose tackle position, as all of them possess the girth and athleticism to succeed.
The linebackers or "the fuel of the 3-4" as Kevin Greene puts it is going to be the Packers greatest boon or bust. Nick Barnett and A.J. Hawk were considered pro-bowl caliber middle- and weak-side linebackers in a 4-3, but in the 3-4, they will both be asked to man-the-middle of the field.
The edge rushers consist of Aaron Kampman, Clay Matthews, Brady Poppinga, Brandon Chillar, and Jeremy Thompson. It has been speculated that Kampman might struggle in the new defense, however, based on his past as both an All-State linebacker in high school and playing linebacker at Iowa, he should produce well. The same is true of Poppinga, and unless Matthews truly shines, expect Poppinga to win the other outside linebacker spot.
The defensive backfield should remain unchanged as man coverage and zone will be equally implemented to match the strengths of corners Charles Woodson, Al Harris, and Tramon Williams. Nick Collins has established that he is a good center-fielder-type safety. Atari Bigby and Aaron Rouse will alternate according to running and passing downs, as Bigby will be the hulking enforcer ala Troy Polamalu and Rouse will be the ball hawk similar to Rod Woodson.
The biggest concern?
Injuries: This team lacks a lot of considerable NFL ready depth for players like Barnett, Jenkins, and Kampman to go down during the season as raw talents like middle linebacker Desmond Bishop, ends Michael Montgomery and Jarius Wynn, and linebackers Jeremy Thompson and Brad Jones are all still developing in special teams packages.
The pass defense should be good this year, as it was last year with a near anemic pass rush. But if the scheme allows the edge rushers to produce 30+ sacks and quarterback pressures, expect the big bodies in the middle to stop the run, and expect the Pack to possess a top 10 defense to rival the teams in the Black and Blue division.