I like the way the 49ers play run defense. They are disciplined in executing their jobs, they get off of blocks, and they play with great pursuit. That’s what great run defenses are made of and it’s what the 49ers have done in the first two weeks of the season.

Against the Green Bay Packers during week 1, they held them to a measly 3.2 yards per carry while faring even better versus the Detroit Lions — who attempted to have a more balanced offense to keep the 49ers on their toes — by holding them to 3.1 yards per carry. I realize that both opponents don’t have great running games, but the 49ers do have a great defense and tomorrow they will meet arguably the league’s best runner in Adrian Peterson of the Minnesota Vikings.

In week 2, the Lions attempted to run the ball in every direction they could and came up short the majority of the time. A big reason was that everyone did their job on the defense. What I’ve come to realize when watching the 49ers is that other defenses have players that try to do their job and someone else’s. This is a problem because by leaving their assigned responsibilities, a defender actually make his defense worse because the runner is able to find the vacated area of the field and run for a big gain. The 49ers don’t have this issue because they follow the popular football mantra, “DO YOUR JOB”.

The ability to get off of blocks is crucial and exceptionally done by the front seven. In particular, Justin and Aldon Smith have formed a wall on the right side and do a very good job of gaining leverage by playing with a low pad level as well as engaging and disengaging off of blockers. Along with this has come great pursuit after the ball carrier from them and the rest of the defense, which creates a very strong and effective team run defense.

Midway through the second quarter last week all that was on display when the 49ers held lions running back Kevin Smith to a two-yard gain on first down near midfield.

The 49ers were in their 40 nickel package, meaning they had a four-man front and five defensive backs on the field, and Detroit was running to the weak-side of the formation, the left where there was less offensive players, despite their offensive linemen in a pass set (two pt. stance).

On that left side, they had the potential to get hat on a hat and create running room for the ball carrier because it was only the Smiths to that side. The nearest defender, other than the cornerback, was deep safety Dashon Goldson (not pictured) so the Lions had the advantage. To compensate for the lack of an additional box defender, defensive tackle Justin Smith accounted for two gaps — “A” to his left and “B” to his right — from a head-up alignment. ┬áThe same could be said for the middle linebacker, Patrick Williams (53), who had both “A” gaps in between the center and guards. For clarity purposes, I did not draw the additional lines (with the exception of Justin Smith), and instead I drew the defense’s flow to the ball.

49ers prepare for the run.

The most important defender on this four-man line was right end Aldon Smith, who was given the responsibility of “setting the edge”. This meant he was charged with forcing the ball carrier back inside to the teeth of the defense instead of letting him get outside the numbers for a potential big gain. Smith had to play with a strong base and low pad level to hold his ground against the blocker, which he did. Once he did his part, the rest of the defensed did theirs.

Justin Smith read the ball carrier and slide to his right as he two-gapped while the nose tackle held his ground in the middle of the formation and the backside end, also known as the “contain,” made sure the quarterback wasn’t rolling out before crashing down the line of scrimmage. The linebackers were also significant here because Bowman (53) was the supporting defender as he avoided a guard’s block and penetrated into the backfield while the backside linebacker (52) served as the cutback defender. Last of all was Goldson, the deep 1/2 safety, who aggressively attacked downhill from Quarters coverage once he read the run and filled the “alley” to help stuff the runner.

Do your job.

The combination of penetration, technique and execution proved to be too much for the Lions here as the 49ers front six and Goldson bottled up the ball carrier for a two-yard gain.

Bottled up.

That’s what Adrian Peterson and the Minnesota Vikings will have to deal with tomorrow and it won’t be easy.

The 49ers don’t allow many rushing yards or touchdowns because of their great team defense. The key for the Vikings will be to move the line of scrimmage and perhaps use some misdirection to will buy their star running back extra time to find lanes and get into the open field where he’s at his best.