It's the main reason why I wouldn't expect much today.
The 49ers boast the best front seven in the league. Willis and Bowman are the two best ILB's in the league, Justin Smith is Justin Smith, and Aldon Smith is quickly becoming one of the best passrushers in the league. Not to mention guys like Ray McDonald and Sopoaga, who are rock solid contributors.
Sanchez has looked completely lost everytime he's faced a top notch defense like Baltimore. And San Frans defense makes Baltimore's look ancient.