49ers defense has been very "collapsy" since end of last season

I just wanted to add a little addendum (wait, that's redundant, isn't it?) to the recap of last night's game between the Seahawks and 49ers. Since most of you are Seahawks fans and rarely seem to care about anything I write about the rest of the NFL, I'll make it quick. But since you know that the 49ers are our greatest threat, I figured you'd want to be privy to something I just realized.

The Niners defense hasn't been very intimidating lately.

The NBC broadcast team pointed out last night that since Jim Harbaugh and defensive coordinator Vic Fangio came to town in 2011 that the defense has been one of the very best in the league. That's quite true, overall, but this is a "what have you done for me lately?" league and the 49ers are starting to separate themselves from the time that they were truly dominant.

Over the first 31 games of the Harbaugh era, including playoffs, the most points that San Francisco had allowed was 32. That was a 36-32 victory over the Saints in the 2011 playoffs and really an aberration to what the Niners had shown all season long. San Francisco was the number two scoring defense in 2011 and allowed 14.3 points per game. The most they had allowed in a game was 27, and they had held opponents under 20 points 11 times.

So over those first 31 games, the 49ers allowed an average of 15 points per game exactly. In a stretch between Week 4 and Week 8 of last season, the Niners held four of those five opponents out of the end zone, including a 13-6 win over Seattle.

And then Week 15 happened.

San Francisco led the Patriots 17-3 at the half and looked well on their way to asserting further dominance over an NFL powerhouse, but then Justin Smith got hurt. New England scored 31 points in the second half, but the 49ers held out for the 41-34 win.

The following week, they lost 42-13 to the Seahawks.

Having allowed 30+ just once in Fangio's first 31 games, the Niners allowed 30+ in four of their last six games, including playoffs. Since allowing 15 points per game in the beginning of the Harbaugh era, they've allowed 29.375 points per game in eight games since. Their best defensive effort in that time span has been allowing 13 points to the 2012 Arizona Cardinals offense, and that's not much of an accomplishment.

Of course, there are plausible reasons for this.

They have played the Seahawks twice, the Packers twice, the Falcons, the Ravens, and the Patriots. Those are all good offenses and it's understandable why a team like San Francisco would have a harder time stopping them than they would, say, the Cardinals.

However, I'd also point out that over a full season's pace, that would be 470 points allowed. The Titans allowed the most points last season: 471 points.

Notable changes this year are the losses of Dashon Goldson, Isaac Sopoaga, and Ricky Jean-Francois. They were replaced by players like Eric Reid and Glenn Dorsey, plus the acquisition of Nnamdi Asomugha. That's where the news get worse for San Francisco.

Reid may have a concussion following a hit on Sidney Rice. Nose tackle Ian Williams has a broken ankle. Ray McDonald also left with an injury, but x-rays were negative. And Nnamdi did not look good from what I saw last night.

It's early, but the Niners are currently 27th in scoring defense after games against the Packers and Seahawks. Is it just a stroke of unlucky scheduling against formidable opponents or is Harbaugh and Fangio's reign of defensive terror over? What do you think?

The 49ers take on the Indianapolis Colts in Week 3.