San Francisco was fresh off a bye and hosting a familiar division foe at home. And regardless of the injury to Alex Smith, one would think that it would have been advantage 49ers.
In order for that to happen, San Francisco's "world class" defense needed to show up though, and for a third time this season, they didn't. Once again they could not stop the run, and even allowed a Steven Jackson rushing touchdown.
They were getting blown off the line and were well shielded from the ball carrier. The pursuit by San Francisco's defense was uncharacteristic, as they struggled to get off the field, and were gashed multiple times.
At the core of the defense, Patrick Willis and NaVorro Bowman could have had much better games. The 49ers defensive line also failed to exploit the Rams offensive line. San Francisco's front seven was permeable and St. Louis asserted themselves.
The problems did not end up front either.
After whiffing terribly on a press coverage assignment, Chris Culliver shouldn't be surprised to find himself on C'Mon Man this week. Between Culliver's error and the lackluster play up front, the Niners started this game down 14-0.
Not exactly the M.O. of the 49ers defense.
Rams wide out Danny Amendola provided serious issues for the 49ers secondary. In his first game back from a shoulder injury, Amendola looked unstoppable in Week 10. And while he is a very good receiver, this is a San Francisco team that has already faced and toppled the receiving corps of Green Bay and Detroit.
Heading into this game, the Rams offense should not have had a chance.
So, what is going on with the 49ers defense?
It's really hard to say. The talent is there and most analysts would probably say not much has changed, but after seeing how flat they came out against the Rams, Vikings and Giants this season, one has to wonder if this is a trend or an avoidable issue.
The 49ers are the caliber team they are largely because of their defense. If San Francisco does not have this imposing defensive unit on game day, they are an average football team.
Luckily, the Niners D has not come out flat in back-to-back games this season. So hopefully, this hair-raising performance will be the last one of 2012. But if it's not, what can the Niners do to combat these sorts of issues?
This also raises a bigger concern: If the 49ers defense is not the 49ers defense, then Alex Smith might not be a suitable QB.