Michigan’s defensive coordinator, Scott Shafer, resigned this week. He resigned his post and he’s resigned to leaving Ann Arbor as the official anti-hero of the 2008 season. He’s an easy target: his unit returned most of its starters from a successful 2007, but the defense performed far, far worse in ’08.

Before the season, when skeptics suggested that it might take a while for Rich Rodriguez to get the spread option running well, Shafer’s experienced defense was was supposed to be the answer.

It didn’t work.

What’s more, Shafer and Rodriguez clashed over schemes, with Shafer advocating the aggressive 4-3 front he employed at Stanford and Western Michigan, and Rodriguez pushing the 3-3-5 he ran at West Virginia.

When he was hired, Shafer told Jim Carty of the Ann Arbor News that “Scheme is overrated, I’ve always believed that. What’s not overrated is getting your kids to play with great effort, great attitude and great enthusiasm.”

He may feel differently now. After allowing 28.9 points per game—the worst mark in the Wolverines’ history—and personally coaching the cornerbacks who anchored a porous secondary, he’s probably searching for answers, and he’s at least searching for a job.

But looking forward, the issue isn’t Shafer anymore, it’s Rodriguez. There are echoes here of Rod Marinelli and Mike Martz—a head coach hiring a star coordinator and then learning on the job about serious philosophical disagreements. (Generally, when are there striking similarities between your elite, tradition-rich football program and the Lions, it’s a bad thing.)

If Rodriguez fields another ineffective defense, it’ll be his job on the line. How will he make this hire? Angelique Chengelis speculates about candidates in the Detroit News, and both names she mentions are known quantities for Rodriguez: U-M linebackers coach Jay Hopson and Jeff Casteel, Rodriguez’ D-coordinator at West Virginia. Casteel is still with the Mountaineers. (MGoBlog has a longer list.) That’s significant, because Rodriguez’ last hire was a stranger.

Rodriguez and Shafer didn’t really know each other before they went to work together. Rodriguez was attracted to Shafer’s Midwestern connections and strong track record, but there wasn’t much of a prior relationship, let alone experience coaching together. It will be telling if Rodriguez now chooses Casteel, for instance, who may make an impact on the field by having a better idea what Rodriguez wants, but leaves the staff with even less of a Midwest pedigree. That’s a dangerous thing in the current recruiting climate, which is already decidedly Greener for in-state prospects.

On his way out of town, Shafer’s final contribution to U-M is taking the heat for a lost season, something he is doing gracefully, if hyperbolically. He told the Detroit News he’s taking “full responsibility for the demise of the Michigan program.”

That’s ridiculous, of course. But if Shafer’s replacement can’t fix the defense, then it won’t be quite so far-fetched—at least when it comes to the Rich Rodriguez era.