There's going to be fierce competition along the defensive line and multiple combinations used to keep those guys fresh. The starter may very well end up with fewer snaps depending on how things are going throughout the game.
IMO many that feel the Pack is down because of the guys "up front" are not considering all of the factors regarding the defense. They look at the numbers and place much of the blame for the poor run defense on the D linemen. The scheme calls for them to occupy, placing the responsibility for shutting down the run on the LB's.
So are the defensive lineman not doing what they are called on to do effectively, or, were the LB's not getting it done, or, both?
Most often last year I thought the interior line did a good job between the tackles. There wasn't much there. Outside the tackles was a different stories which leads me to believe it was the LB's not getting it done.
Regardless, the play along the interior line should improve and we will have more experience there with some young guys getting valuable PT last year.
The competition there will make them all work harder as well.
The big upgrade in the Lb position is where I see an improving run defense from where it was last year. Speed and anticipation. Something we lacked last year and IMO what contributed to our lousy run D more than the interior line play.