By Dan Durkin-

(CBS) In 2013, the Minnesota Vikings accumulated 41 sacks for the entire season. Through nine games this season, they already have 30, good for third in the league.

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There are a few reasons for their spike in pressuring opposing quarterbacks, starting with their hire of Mike Zimmer as head coach and the subsequent moves they made in the offseason.

The Vikings retained defensive end Everson Griffen, signing him to a rich $42.5 million contract with $20 million guaranteed the day before the free agency period. The numbers of his deal raised eyebrows around the league, but he’s quite the talent, and his early season productivity — nine sacks in nine games, third in the league — has been exactly the type of return Minnesota was looking for on the lucrative extension.

In the draft last May, the Vikings used the ninth overall selection on UCLA standout Anthony Barr. In college, Barr was an outside linebacker in a 3-4 scheme and displayed the characteristics scouts covet — leverage, length, size and strength. For the Vikings, Barr has made a seamless transition to the strong-side (Sam) linebacker spot and plays a crucial role in their pressure packages.

Zimmer has always been fond of stockpiling athletes along the defensive front with complementary skills. By using a rotation, he’s able to keep players fresh, and he’s very adept at scheming one-on-one situations for his rushers. One of the staples of his pressure package is the “mug” look, whereby he aligns his linebackers on the outside shoulders of the center to create pre-snap conflict in the protection scheme, then plays line games post-snap to further complicate matters.

Post-snap, Zimmer plays hybrid coverages behind the blitz — depending on how many rushers he actually sends from the mug look — to confuse the quarterback’s reads.

Let’s go to the film room to take a closer look.

The first example comes from the Vikings-Bills game. On a third-and-5 in their own territory, the Bills come out in 11 personnel in a doubles slot gun formation. The Vikings respond with nickel personnel and show a seven-man defensive line, walking safety Harrison Smith up to the line and mugging the A-gaps with Barr and Chad Greenway.

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With four rushers to the offense’s right, the Bills must slide their protection to the right and create a three-man blocking surface, in case the Vikings send everyone they’re showing pre-snap.

But the Vikings bluff with their blitz and drop Smith, Barr and Greenway as the underneath defenders who play a matchup zone, while the rest of the secondary plays man coverage.

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With the tight end releasing on a route and the running back on a check release (staying in unless there are no blitzers), the Vikings have single blocks on the offense’s left side, where they run a T-E or “tex” (tackle then end) stunt, to get a free rush for defensive end Griffen.

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Griffen zeroes in on Bills quarterback Kyle Orton, dropping him for a six-yard loss on the sack.

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The next example comes from the Vikings-Redskins game. From this mug look, the Vikings send both linebackers and run two stunts. They run the same “tex” stunt with Griffen, but they also stunt the linebackers sending Barr first with Greenway trailing over the top.

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With the running back Roy Helu off-set to quarterback Robert Griffin’s left, the Redskins slide their protection to the right, which leaves only three blockers versus four rushers.

Helu attempts to pick up Barr but is defeated at the point of attack as Griffin is dropped for a loss.

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The Vikings pose a huge challenge to the Bears’ offensive line, which has allowed 24 sacks on the season. Communication and being assignment sound will be critical, as well as being able to hold up in one-on-one situations to keep a clean pocket for quarterback Jay Cutler.

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Dan Durkin covers the Bears for CBSChicago.com and is a frequent contributor to 670 The Score. Follow him on Twitter at @djdurkin.