Edit:  Made this a Diary after a couple of kind requests.  Lest my psyche be further questioned, I'm M-Pragmatist here...and I think M-Optimist is slightly bats(hit insane... like, asylum-worthy).

M-Optimist on the DL: 

The D-Line will be the strength of the D, lead by Death Roh and Martin.  Yeah we lost BG, but these two are beasts, and they return faster, stronger, bigger, badder or as I like to call it, barwisier.  On top of that, Big Will is ready to step up, RVB is a quality vet, and three solid seniors provide depth.  Depth makes up for the loss of BG.

M-Pragmatist on the DL: 

For all the BG-love, the logic above makes him sound replaceable. Despite double and triple teams, BG still managed to make impact plays in every single game. He killed drives single-handedly and turned TDs into FGs.  No one is replacing that.  Roh and Martin are quality players but they’re not all-confrence caliber.  Furthermore, without BG stealing attention and absorbing blocker's attentions, their effectiveness is going to be limited.

Campbell, for all his hype, has been completely ineffective.  He’s only a true sophomore so of course it would be extremely premature to call him a bust.  But, it's also extremely premature to assume he’ll be an impact player.  The ho-hum upperclassmen remain ahead of him on the depth chart.

While the DL is probably the strength of the defense, it's likely taking a significant step back with the loss of someone of BG's caliber.  The depth and returning experience is nice, but this is most likely an average B-10 defensive unit.

M-Optimist on LBs:

Ezeh and Mouton return for their senior year, when players typically have their best season.  Moundros may be inexperienced, but he should be a good run-stuffing role player.  Fitzgerald and Demens are coming on.  With GERG coaching them and another year of experience, the LBs won’t be as bad as last year.

M-Pragmatist on LBs:

You forgot to mention Stevie Brown, arguably the 2^nd best defender last year. Browns was a talent who has been extremely impressive in NFL camp.  Replacing him is a position-switch red-shirt freshman.  This is the biggest downgrade (after CB) on the defense and it’s consistently ignored or underplayed by M-Optimist.  We had a talented, versatile, senior LB who is playing in the NFL…now we have a guy who played QB for most of high school and hasn’t played yet in college.

As Brian has noted, Moundros being a potential starter should set off alarm bells for the rumored improvement of Ezeh.  Some guys just never get it.  The ILBs should be better, this is true…but the loss of Stevie Brown is going to hurt this unit.

M-O on the Safeties:

There is finally some talent and depth back here. Gordon and Robinson are skilled.  Kovacs and Emilien return with a year of experience.  I know they’re young and they’ll make some mistakes, but these young guys will be better…it can’t be as bad as last year.

M-P on the Safeties:

Its true, probably won’t be as bad as Kovacs/Williams.were last year.  But consider that last years corners were Woolfolk and Warren.  This experienced duo allowed the safeties to take a little less responsibility.  This season, the CB situation is a tragedy, and the safeties will be asked to do more. 

One of the most experience-dependant positions on the field has almost none. Gordon and Robinson have not played.   Kovacs is still a walk-on type with limited skill, even if he has a year of experience. Emilien still can’t beat anybody else out on the depth chart, where walk-ons remain on the fringe.  To see such extreme inexperience and expect significant improvement is being willfully blind to history.

M-O on CBs:

Losing Woolfolk sucks but it won’t cost us as many games as we think.  Floyd is better.  Cullen and the other freshman are going to step it up.

M-P on the CBs:

Woolfolk probably won’t cost too many games, this is true.  What many forget is that Woolfolk wasn’t exactly a lock-down CB to begin with: A 3-star talent who proved capable last year, but was far from all-conference.  He was an excellent player only relative to the other choices. Furthermore, the Cullen hype is insane.  Freshman CB, even the HOF-caliber guys we’ve had in the past, struggle as freshman. 

I won’t go on.  Its bad and we all know it.  This unit alone can submarine whatever other gains you want to hope for from others.

M-O on continuity:

Yeah, yeah, there may be concerns on an individual basis, but the team the team the team. Another year in the system, Hopson is gone, and the 4-2-5-3-3-5 hybrid D will be an improvement.  You’re only as good as your weakest link.

M-P on continuity:

You’re grasping at straws.  Most other teams return with another year of experience in their defensive system with almost no upheaval.  This is not an advantage for Michigan, its avoiding a major disadvantage.  The shift in terminology and pseudo-shift in system is not an argument for improvement, no matter how many off-season fluff pieces you’ve read.

The weakest-link argument is highly suspect, but even if you buy it, the 2009 safety disaster is no worse than the 2010 CB tragedy.  Outside of that positional weakness, the 2010 impact players aren’t nearly on the same level as BG, SB, DW, and TW.

M-O on luck:

Last year, we were a couple plays away against Iowa and MSU.  And Illinois, ugh!...we had that game.  Should have had 7 or 8 wins and this years offense is even better.

M-P on luck:

We also eked by ND and Indiana - a couple plays from 3 wins again…and this years defense is even worse.  M's on field luck is neutral.  Every fanbase thinks they're unlucky...except that private school in Indiana.

M-O on fate and talent:

You’re wrong…this just have to get better…they just do.  Rich Rod knows what he’s doing and in year 3 things will be better.

M-P on fate and talent:

I hope you’re right.  And on offense, I’m with you.  But the D man, the D…I just don’t want you to scream for Rich Rod's head and call him and underachiever when you don’t get the 8 wins you expect.  At least acknowledge that 5 wins isn’t an unreasonable prediction that only big-dumb-jerk-faced-dummies can have.

M-O on predicting the future:

But M-Caliber did a convincing analysis with regression maths and lots of sig figs and it says we’ll win 7 or 8 games easy.

M-P on predicting the future:

M-Caliber rules, but his model is not predictive for future seasons.  He assumes the defense will be better overall (ypg) and also assumes the D will be way better at creating turnovers.  I suspect this is wishful thinking. The turnover gap should be better via regressing to the mean, but this is still a below average D and once again we’ll have a first-year starter at QB.  (The “if Denard throws INTs he’ll be on the bench” line is questionable.  We know Tate will too.)

M-O on think-good-thoughts:

Man, why are you such a hater?  I’m just trying to think positive.  This will help the team. Good vibes matter!

M-P on think-good-thoughts:

Bo hated hippies.

M-O predicts:

Whatever, I say we're due for some good luck and we get 8 wins.  What do you think, smartass?

M-P predicts:

6 wins, assuming we beat UConn.  But I think we'll get completely embarrased in a couple of the rivalry games, which is going to spawn some serious unrest in the unreasonable realms of the fanbase. I actually think 5 is the rational prediction and that 6 or 7 is being an optimist...8 or 9 is just wishful thinking.