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The elite Green Bay Packers run defense that showed up in the first quarter of the 2013 season went off the rails by Week 17—but if the team prioritizes re-signing certain free agents and picks up a couple key players in the draft, the unit can be stout in 2014.

Through six games in 2013, Green Bay had the No. 3 run defense in the NFL, having allowed an average of 79.0 rushing yards per game to that point.

By the end of the regular season, they were No. 25 and allowing 125.0 yards on the ground per game, and an average of 4.6 yards per attempt.

What went wrong? And more importantly, looking forward, how can the team start strong against the run and avoid the steep drop-off next season?

A combination of factors were likely culprits in the decline of the rushing defense. The schedule is a big one. Beginning in Week 8, the Packers faced a string of three of the top five rushers in the NFL at that point: Adrian Peterson, Matt Forte and LeSean McCoy.

Another often-underestimated factor was the injury to Aaron Rodgers, after which the Packers consistently played from behind, allowing opponents to run the ball aggressively to protect their lead and run down the clock. Any run defense would be in danger of folding when opponents are cramming the ball down their throats for entire halves of games.

Looking forward, personnel changes could shore up the unit, while failure to plug in the right pieces could doom it. The Packers have a large number of players who factor into the run defense scheduled to become free agents, both unrestricted (Ryan Pickett, B.J. Raji, Johnny Jolly, Rob Francois, Mike Neal and C.J. Wilson) and restricted (M.D. Jennings and Jamari Lattimore). Additionally, safety Chris Banjo is an exclusive-rights free agent.

Breaking the unit down by position group, the following moves could help Green Bay build a top-three run defense in 2014.

Defensive Line

An excellent nose tackle is a cornerstone of the 3-4 defense, and can be hard to find for both the sheer size and also athleticism he must possess. The Packers have two players set to become unrestricted free agents who have excelled at nose tackle in Raji and Pickett. It's highly unlikely that they'll reach new deals with both.

Green Bay has a few options at the nose. Ted Thompson can choose to retain Pickett, which likely means Raji will be allowed to walk. At 34, Pickett is the oldest player on the team, and it's probable that a new deal for him wouldn't stretch beyond two to three years, meaning the Packers would be in need of a starting nose tackle again fairly soon.

The Packers could also choose to let Pickett walk and move Raji back to nose tackle. He had his most productive season at the position in 2010 and clearly benefits when he is given freedom to rush the passer.

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At the 3-technique position, where he has played since Pickett moved to nose in 2011, Raji's primary responsibility has been to "grab guards," as he told Bob McGinn of the Milwaukee Journal Sentinel this season, because Dom Capers "likes his linebackers clean."

Raji is rarely used in sub-packages, where rising star Mike Daniels has been the defensive end who is given leeway to get after the quarterback and has had a lot of success doing it. He led the team in sacks for much of the season.

Moving Raji back to nose would allow Green Bay to bring in a large two-gapper who would be better served as a 3-4 defensive end, while Raji's potential is maximized in the center of the line.

Green Bay does still have Johnny Jolly and C.J. Wilson to consider, but with four defensive linemen needing new contracts and not all likely to get them, there's no doubt the Packers will pick one up in the early rounds of the draft.

Defensive tackle Ra'Shede Hageman out of Minnesota would be a stellar addition to the Packers' run defense at the 3-technique position. At 6'6" and 318 pounds, he's certainly the right size to push back blockers. If they wanted to wait until the second round to add this piece, Stephon Tuitt out of Notre Dame or Will Sutton out of Arizona State would fit the bill.

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The only reason the Packers should pass up a first-round defensive tackle to shore up the run defense is if they can snatch up a top-rated safety.

Safety

It's very likely Green Bay already has its run-defending safety on the roster in Sean Richardson. Clearly a top safety talent along the lines of Ha Ha Clinton-Dix or Calvin Pryor is needed in the passing defense, but upgrading that area allows the Packers to keep Richardson relatively tethered to the line, utilizing his strongest assets.

Capers has described Richardson as "a big-safety, small-linebacker type of guy," according to Mike Vandermause of the Green Bay Press-Gazette (subscription required), and his physicality is one of his greatest assets.

When the Packers are planning on playing seven-plus men in the box, especially against Adrian Peterson, Reggie Bush or Matt Forte twice a year, Richardson should absolutely figure in.

In fact, Capers' reluctance to start him last season over the clearly struggling M.D. Jennings was likely because he excels so much more against the run than the pass, and in 2013 the Packers didn't have a strong enough safety pool to afford to start a player who didn't excel in coverage.

But no more in 2014; the Packers should and will make adding a strong pass-defending free safety a priority in the draft, which allows Richardson to come in on sub-packages as a run defender.

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Of course, if the Packers are going to spend a high draft pick on a safety, they'll do well to prioritize a complete safety who can defend the pass and the run both. In that case, it's possible Pryor is a wiser choice than Clinton-Dix.

Clinton-Dix has topped free-safety prospect rankings for months, but Pryor's stock is skyrocketing. He's the largest safety in this year's class, at 6'2" and 208 pounds. He can make a huge impact in the box as a run defender, but is also skilled at taking the correct angles on his tackles in space.

The Packers would be hard-pressed to pass up Clinton-Dix if he were on the board at No. 21, but they may get more bang for their buck in terms of beefing up the run defense with Pryor.

Linebackers

Missed tackles plagued the run defense in 2013, and not all of them were on the secondary. A.J. Hawk, despite having a strong season with 71 tackles and four passes deflected, missed 13 tackles, according to Pro Football Focus (subscription required), tied for the fifth most among inside linebackers in 2013.

Against the run, Hawk was 52nd out of 55 inside linebackers graded by Pro Football Focus.

Hawk needs help on the inside, and Brad Jones hasn't yet proven he's up to the task. The Packers need to add a piece here to fortify the middle and help stuff the run.

Green Bay can have its pick there. In the third round, Wisconsin's Chris Borland, Stanford's Shayne Skov and Florida State's Christian Jones will all possibly be up for grabs.

Those doubting Borland for his size will be left in the dark once the 2014 season begins. The 5'11" linebacker more than makes up for his size with his aggression off the snap, consistently getting to the ball and making plays in space. He could be an explosive addition to Green Bay's struggling front seven.

If Thompson wants to go with a safer choice at inside linebacker, Skov is a great one. He can break through the line to make plays in the backfield. He's aggressive and his size is a huge attribute. Stanford's defense allowed fewer than 90 rushing yards per game on average last season, and it was all anchored by Skov.

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If Skov's specialty is bursting through holes to get after the ball-carrier in the backfield, Jones' is making plays in space, due largely to his height and build. He led the national champion Florida State defense in forced fumbles, with two on the year.

Ultimately, the Packers' overarching problem in rushing defense last season was failure to execute. Re-signing free agents who have proven themselves capable in the system (Jolly, Raji), letting hazards walk (Jennings) and making some personnel switches will be a boon to the run defense in 2014. Adding key pieces from the draft ensures the talent level is there, while existing veteran leadership allows the unit to continue to run smoothly and perfect technique.

Having a healthy Matthews next season will be especially beneficial to that last point. He understands what his unit needs to do to get back to its elite status.

"Usually it has to do with missed tackles and technique issues as well as not fitting in your gap," Matthews told ESPN's Rob Demovsky in late November, when the run defense was in free fall. "Obviously it's easier said than done, but we just need to get back to that."

With the right pieces in place for 2014, the Packers will be able to do just that.