From the beginning of the season the D wasn't playing up to last year's standard, even before injuries hit Williams and Collins. I think part of the reason is teams used all the time during the lockout to dissect Capers' D and not only was he unable to surprise teams by using the 2-4-5 with Woodson as the "rover" and his exotic blitz packages; opponents were fully prepared for them.
Remember after the San Diego game when Woodson said Capers has to draw some plays up to free up Clay from double teams? He was basically advocating for a more aggressive scheme on defense. IMO knowing they can rely upon the best offense in the league, the Packers can emphasize one of two defensive schemes: One is "bend but don't break" which puts pressure on opposing Os not to make mistakes as they drive down the field. The benefit should be limiting the number of explosive plays and forcing teams to attempt FGs; the disadvantage is opponents can eat up the clock, keeping Rodgers & weapons off the field. This is the style of play the Bears under Lovie Smith generally use, with an emphasis on causing fumbles. That's what I think Capers was doing through the San Diego game, only with an emphasis on INTs. The other way to go is attack opposing offenses relentlessly. The benefit is turnovers are more likely as are stops after big plays on D. The disadvantage is that style allows more explosive plays. Either way, opponents get stopped more quickly, score more quickly, or turn the ball over and they won't be as likely to eat up the clock and Rodgers & weapons will get plenty of opportunities. Don't get me wrong: Every team uses a combination of these tactics; I'm talking about the emphasis of the D scheme. Of course Capers would prefer getting consistent pressure on the QB rushing four and keeping seven back in coverage. But they haven't been able to do that consistently - most NFL teams can't - so IMO one of the other options has to be emphasized. I favor the latter: A "quick strike" defense, even with its disadvantages, to go along with the quick strike offense because let's face it, the team relies upon, and will continue to rely upon Rodgers & weapons. I think Capers has been going more and more to that scheme. The pressure on Manning Sunday is the latest example.
BTW, I disagree about Collins - I think his loss is extremely significant. Morgan Burnett is very athletic for a safety IMO but Collins is even more so: He's got CB speed in a safety's body, he makes plays on the ball, he knows the D's Xs and Os inside and out, and having started since he was drafted in 2005, his experience is invaluable. I have the feeling he helped the CBs by covering up mistakes even more than we knew. (Thompson's first two draft picks as Packers' GM: Rodgers and Collins!)
BTW #2, Hawk is the "QB" of the D - one of the reasons they let Barnett go was how well Hawk adjusted to that role after Barnett got hurt.