The defense with Arrington outside and Chung-Gregory at safety isn't going to dominate a Pop Warner game, so I make no judgments based on the Jacksonville debacle.
The transformation of San Francisco's defense from averaging 14PPG to giving up 73 points in the last 5+ quarters since Justin Smith got hurt shows how much an injury to a single key player can affect a defense. Prior to that point, San Francisco had played the entire season with 10 starters playing over 92% of the defensive snap count (DBs Dashon Goldson, Donte Whitner, Tarrell Brown and Carols Rogers; LBs Patrick Willis, Navorro Bowman, Aldon Smith and Ahmad Brooks; and DLs Justin Smith and Ray McDonald). Great players, but it's a heck lot easier for a defense to be "dominant" with that kind of continuity. The Pats have had only 2 players play only 90%+ of the defensive snap count this season - Jerod Mayo and Devin McCourty, and McCourty has had to flip flop positions all season.
I'm fairly confident that this defense at full strength can be quite good. I don't have much confidence in this defense when it's patched together with band aids and guys playing out of position.
Jones showed signs of finally re-gaining his early form. Cunningham will be back. The DL should be at full strength going into the playoffs barring injuries this week.
Spikes was out against Jacksonville, and that hurt. Hopefully he will be fully healthy for the playoffs. Hightower is rounding into form.
The secondary is the biggest question. We need Talib and Dennard healthy.
Let's see how things look after this week, and re-assess.
So let's try an exercise in reverse analysis:
- Since drafting Aldon Smith and acquiring FA Carlos Rogers in 2011 along with re-signing FS Dashon Goldson and the maturation of Navorro Bowman into an impact player, the 49ers' defense allowed an average of just over 14 PPG throughout the 2011 season and for the first 13 games of the 2012 season. As mentioned above, they had the good fortune to be able to have 10 of their 11 starters play over 92% of the defensive snap count for those 13 games this season. They held the most prolific offense in the NFL to 3 points for most of 3 quarters in game 14.
- Since Justin Smith injured his elbow against the Patriots, the 49ers have given up 73 points in slightly more than 5 quarters.
What has causes such a drastic change in a dominant defense? In an interesting piece, Bucky Brooks of NFL.com looks at some of the issues behind the "collapse" of the San Francisco defense:
San Francisco 49ers' defense falling apart without Justin Smith - NFL.com
Brooks' analysis focuses on 3 basic elements:
1. Offenses running the ball at Aldon Smith.
2. Easier ability for offenses to scheme against Aldon Smith in pass protection with Justin Smith setting picks for him against opposing guards.
3. With the pass rush neutralized, it has been much easier to attack the 49ers secondary and straightforward man coverage schemes.
What's interesting about this analysis is that it shows the kind of "domino" effect that we saw with the Aqib Talib trade, but in reverse: take away one key player, and the entire nature of the defense changes dramatically.
Looking at the Pats' defense - assuming that Talib and Dennard stay at CB and McCourty at FS for the long term - it would seem to me that if the Pats had succeeded in getting a guy like Red Bryant (or even Jonathan Fanene, had he been able to play as expected) who had been able to play outside or inside and generate a combination of effective run stopping and outside and inside pressure, that it would have had a similar impact on the overall effectiveness of the defense. Imagine what a Calais Campbell or a Henry Melton (who came out as a defensive end) could do. Even a rookie like Ziggy Ansah, Sam Montgomery or Sheldon Richardson could potentially have a significant impact.
For people that think are skeptical that this defense might only be 1-2 players away from being dominant, it's interesting how the loss of Justin Smith - just 1 player - has transformed the 49ers defense from giving up 14 PPG over the previous 29 games to averaging 38 PPG over its last 2 games.