San Francisco 49ers' defense, then and now

San Francisco 49ers defensive coordinator Vic Fangio tends to resist lazy narratives even when they're self-serving.

It's one of the attributes that can make Fangio a good resource for how well the 49ers' defense is playing at a given time.

2011-2012 San Francisco 49ers Defense

Before the 2012 season, Fangio was honest about some of the factors beyond his control that contributed to the 49ers' stellar defensive statistics in 2011. He credited the 49ers' offense for avoiding turnovers. He credited the offense and special teams for contributing to favorable field position.

Now, as the 49ers prepare for their first Super Bowl performance since the 1994 season, Fangio is resisting suggestions that halftime coaching adjustments were key in limiting Green Bay and Atlanta to 10 points in the second halves of two playoff games.

"I think sometimes that's overplayed," Fangio told reporters. "We called the game just a little bit different, but not a lot. Basically, our guys just played better in the second half."

I'm likewise not going to read too much into statistical changes for the 49ers' defense from last season to this season. Those appear in the chart. On the surface, it appears as though the 2012 defense has slipped in the red zone and against opposing quarterbacks.

A two-game stretch against New England and Seattle accounts for some of the change in percentage of touchdowns allowed on opponents' red zone possessions.

The Patriots and Seahawks scored eight touchdowns in nine red zone possessions over six quarters and eight days against San Francisco. The 49ers played nearly all of that span without Pro Bowl defensive end Justin Smith, who has since returned from injury. Those games were played on the road and on opposite coasts, both in prime time against playoff teams.

San Francisco allowed 17 touchdowns in 40 red zone possessions during the 2011 regular season and playoffs. The 49ers allowed 25 touchdowns in 42 possessions through 18 games this season. That includes three touchdowns in six red zone possessions during each of the two postseason runs.