Reading this article at Pro Football Focus on the top 10 defensive ends in a 4-3 alignment (obviously it doesn't include any Green Bay Packers because the Packers play in a 3-4 alignment) made me think back on the past two seasons under Dom Capers.
Here are the Packers defensive rankings over the past three seasons. 2008 was the last season in a 4-3 under former defensive coordinator Bob Sanders. Rankings from Football Outsiders:
Season Pass Ranking Run Ranking
2008 7 28
2009 4 5
2010 1 16
Sanders was partially a victim of injuries in the secondary, and the mid-season loss of LB Nick Barnett, but that 28th overall run defense was well deserved. It was awful in 2008.
In 2009, the run defense's improvement in the new 3-4 was immediate and lasted throughout the season. It was a remarkable improvement, and it turned me into a believer.
But in 2010, the run defense slipped. Some of that was by design, as Capers often called for only two defensive lineman to sacrifice some run support for pass coverage. Maybe some of the blame can be placed on individual defenders, but run defense is as much about supporting the overall scheme and all the defenders have to take part of the responsibility on a stop. One player might hold the line, but it's useless if someone over pursues and opens a cut-back lane.
Defense is a lot about having the players to make plays. The Packers aren't going to switch back to a 4-3 because they don't have the personnel to do it, and Capers is a 3-4 defensive coordinator who probably isn't as effective in another alignment. But I think the players are responsible for the defensive improvement, and I'm not as sold on the 3-4 alignment as I was a year ago.