Here's an article by McGinn about the interior d-line setting the tone against the run and transforming the defense. Without Hawk to keep clean behind them, the d-line is more free to penetrate and make plays on ball carriers to force tougher down and distance situations and then unleash the pass rushers.

Protecting the inside linebackers was a way of life for the defensive linemen of the Green Bay Packers in their first six years under the current coaching staff.

It was the only way coordinator Dom Capers probably thought the run defense could hold up with A.J. Hawk and other lightweights stationed at inside linebacker.
For a multitude of reasons, the run defense died from Game 8 on in 2013 through Game 8 of 2014. In those 18 games, foes rushed for 156.1 per game and 5.01 per carry.

In 14 games with Matthews inside, those totals are 106.4 and 4.26. If you care to throw out the 199 yards gained by quarterbacks this year, the four-game yields are 65.3 and 4.02.