Packers run defense
This would have been a cause for concern even if the Packers were healthy, but they're not healthy. Last year's leading tackler, Desmond Bishop, is out for the season with a torn hamstring that required surgery. Underrated from a national perspective, Bishop ranked in that second tier of inside linebackers behind the likes of Patrick Willis and Ray Lewis. He was a tackling machine, big hitter and big-time playmaker. Nose tackle B.J. Raji and defensive end Ryan Pickett will start but probably aren't 100 percent. Raji turned an ankle during the preseason finale and Pickett missed time with a calf strain.
Bishop has been replaced by short-but-sturdy D.J. Smith. Smith's a tackling machine, as well, but he's not a big-time playmaker. The other inside linebacker is A.J. Hawk, who the Packers took No. 5 in 2006 while San Francisco took Vernon Davis at No. 6. Hawk didn't create a single turnover last season and lacks sideline-to-sideline speed. The Packers ranked 26th with 4.7 yards allowed per carry. They'll have to do better to put the game on the shoulders of Alex Smith. The Packers had their hands full in last year's opener against Darren Sproles; it will be interesting to see if Jim Harbaugh tests the defense with Kendall Hunter or LaMichael James.
49ers run offense
The 49ers will look immediately to set the game's tempo on the ground, and they will come right at the Packers, seeking the soft spots in the Green Bay defense with a power rushing attack. San Francisco's ground game is the unquestioned strength of the offense, and that doesn't look to change much, even though the 49ers have several new weapons in their passing arsenal.
The Niners will attempt to run between the tackles with mauler left guard Mike Iupati pulling often to lead Frank Gore and Co. through the holes. Iupati is quickly becoming one of the best run-blocking guards in the league, and San Francisco's line works well as a unit in that department with tackles Joe Staley and Anthony Davis and center Jonathan Goodwin joining a new starter at right guard, Alex Boone, the team's No. 3 tackle last year. The Niners have an outstanding run blocker in tight end Davis, and the Packers will see the Niners coming at them with several two-tight end alignments. Young fullback Bruce Miller also is a key ingredient in the mix.
The whole operation revolves around the churning, slashing, power-bursting runs of Gore, the NFC's third-leading rusher last season who made it to his third Pro Bowl after becoming San Francisco's all-time leading career rusher. The Packers will get a frequent change-of-pace dose of Hunter, who is elusive in the open field but can run between the tackles. Green Bay may even see backup quarterback Colin Kaepernick entering the game to direct some wildcat formations that could feature slippery rookie James.