It's the defense stupid. That's the main reason for Michigan's turnaround in 2011. You can see the trend quickly in chart form courtesy of /r/cfb. If you'd prefer long-ish form Andy Bitter has you covered.
Oft-criticized defensive coordinator Greg Robinson had never run the 3-3-5 scheme former coach Rich Rodriguez preferred and was forced to work with many of the assistants Rodriguez brought with him in 2009-10. The Wolverines' defense, which had always been stout under ex-coach Lloyd Carr, dropped from 24th nationally in Carr's final season to 82nd, 67th and 110th in Rodriguez's three years.
Enter Mattison, who used to coach at Michigan, Notre Dame and, most recently, the NFL's Baltimore Ravens from 2008-10.
A proponent of the 4-3 defense, Mattison's scheme better suited Michigan's personnel, with defensive lineman Mike Martin (54 tackles, 5.5 TFLs, 3 sacks) and Ryan Van Bergen (41 tackles, 12 TFls, 5 sacks) starring up front.