Many of the Packers issues in 2008's 6-10 season can be directly attributed to the defensive side of the ball. The Packers ranked 20th in overall defense and could never seem to get an important stop when they needed it, losing seven games by four points or less.
At the end of 2008 defensive coordinator Bob Sanders was let go, and after an lengthy search for a new coordinator, the Packers settled on Dom Capers.
Capers brought a 3-4 defensive scheme to the Packers and there was some concern over whether or not the Packers had the right personnel to run a 3-4 scheme.
Although the Packers had a couple of defensive lapses in 2009, most notably in a playoff loss to Arizona, the defense adapted rather quickly to the new scheme and the Packers ranked second in overall defense and led the league in turnover ratio. Barring major injuries there is no reason to believe the Packers won't duplicate that success in 2010.