The immovable object meets the unstoppable force this weekend as the Green Bay Packers run defense takes on Ezekiel Elliott and the Dallas Cowboys top-ranked running game.

The Packers are currently locked in as the second best run defense according to Football Outsiders DVOA metric and ranked first overall statistically on NFL.com with the fewest total yards allowed (171), lowest yards per carry average (2.0), lowest yards per game average (42.8) and has not allowed a run over 14 yards on the ground.

This week they see Elliott, who leads the league in total yards (546) and has a healthy 5.0 yards per carry average.

Not only is Elliott a tremendous back, but he takes handoffs behind one of the best offensive lines we’ve seen in some time. The Dallas Cowboys front five are an excellent group and even when they are dealing with injuries, as they are now, the depth steps up and performs.

For the Packers, this season marks a large improvement over the past few seasons, including last year when they ended the season with a so-so 12 ranking against the run.

This will be their greatest test so far this season, since Adrian Peterson lasted only part of the game in Week 2 against the Vikings.

A large portion of the success the Packers run defense has had—and what it will continue to need to contain Elliott—comes from the initial push along the defensive line, particularly Mike Daniels and Letroy Guion at the tackle spots. Both players have been getting tremendous push against offensive lines and clog up the interior holes very well. Meanwhile the edge rushers—a combination of rookie defensive end Dean Lowry and linebackers like Clay Matthews and Nick Perry (who is finally showing us what was expected of him coming out of USC in 2012)—have done a great job of containing runners and preventing them from getting outside when the interior is clogged up.

It also has involved solid play by the inside linebackers, chiefly Jake Ryan, rookie Blake Martinez and backup Joe Thomas. They vacillate between stepping in immediately to jam up the running lanes the front line doesn’t and hanging back a moment to read the play and see where the ball is, before flying in that direction.

Naturally, the safeties and corners have been involved, but this all is a success in large part because the front seven has been nearly perfect in fulfilling its responsibilities.

The front seven has repeatedly gotten penetration along each offensive line they have faced, often hitting the ball-carrier in the backfield before he can get a head of steam. There are the occasional breakdowns and tackling misses, but for the most part when they hit, they finish.

The Packers also appear to be able to defend the run regardless of offensive formation. Looking at the tape, teams have tried to overpower them with bunch formations and extra blockers up front, spread them out with multiple receivers, and added a fullback to block but nothing seems to phase Green Bay. They know their role and have been executing well regardless of both formation and down and distance.

Again, they face a very tough test this week. The Dallas offensive line has been opening up massive running lanes for Elliott the last few weeks and once he’s in the open field it’s a problem.

Nick Shook of NFL.com did a nice breakdown of how the Cowboys are creating these creases for Elliott and how the rookie is taking advantage. Shook talks about how Dallas sets Elliott up for his long runs, using good blocking tight ends, movement from the receivers and a great job by the offensive line of getting to the second level to block linebackers and safeties.

The Packers will have to be extra careful to stick to their responsibilities and not get sucked out of position. The Cowboys have been great at scheming around the opposing defense’s strengths to put Elliott in a positon to succeed. The Packers will be hard pressed to stop them, but what we’ve seen so far this season leads one to believe they should be up to the task.