Jeff: Deion Barnes The quarterback is, uh, the quarterback of the offense, yet I went with a left tackle as the most irreplaceable player. Without a great left tackle, the QB is toast. Similarly, on defense, the middle linebacker is very often the "quarterback of the defense", but without a dominant edge rusher to get pressure on the opposing quarterback, the Penn State defense struggles. This defense is predicated on the front seven getting to the QB early and often, and Barnes provides a great, young talent at the defensive end spot. Like Smith, any mistakes he may have made in his redshirt freshman season can be chalked up to inexperience and youth. But the mistakes were already few and far between, so without Barnes in 2013, the defense would likely struggle.
Ben: Adrian Amos I spoke with Rick Pitino to get his thoughts on this question. Per Rick, 'Gerald Hodges isn't walking out of that locker to play nickle corner this season.' Translation: Ron Mercer Adrian Amos. It would be very difficult for an extremely young secondary to lose its most versatile piece. He can play inside or outside as a corner; strong or free as a safety; and he's the best tackling, most physical DB on the roster. Amos brings a little mautiness to the defense. And he's also the best kick returner on the team; is a leading tackler on kickoff, and probably plays a mean banjo at a bluegrass festival.
Jared: Mike Hull Replacing two stud outside linebackers is no small task. Fortunately, Hull should be able to step in and provide the production that Gerald Hodges and Michael Mauti are leaving behind. Hull has some mighty big shoes to fill, but he proved in 2012 that he has an excellent nose for the ball and big-play ability. He should shine in 2013 once he is elevated to a full-time starter. As Penn State breaks in a more inexperienced OLB on the other side of him, the success of the defense will oftentimes hinge on Hull's performance.
Cari: Glenn Carson Here's where I follow the rules. Carson is perhaps the least heralded MLB to play for PSU in quite some time--and, by all accounts, that's how he likes it. I expect him to be a quiet leader on the team, leading by example and modelling on and off the field behavior for the younger guys. He's been overshadowed his entire career, by Mauti and Hodges, and even by Hull. But if he's gone, our scary depth at LB would be an even more glaring weakness.
Dan: Adrian Amos The secondary progressively got better throughout the year and Amos and his versatility was a big part of that. Amos will be the leader of the secondary next season with Stephon Morris graduating and John Butler focusing on the entire defense now as coordinator. Combine that with his special teams duties and Amos may be the most irreplaceable member of the entire team.
Adam: Mike Hull Given what we were operating with last year in terms of depth issues, Adrian Amos should probably be at the top of this list. But have you looked at our depth chart at linebacker lately? The talent is there, but the depth is sorely lacking. That means that our expected playmakers need to deliver, and Mike Hull needs to become the playmaking linebacker we expect him to be. His limited role will need to increase. Our defense is still predicated on great linebacker play, and he's the one that makes the difference between good and GREAT.
Nick: Deion Barnes I'm actually pretty happy with the linebacker and secondary depth, so I have agree Deion Barnes is the call. We'll see how well they reload on the line this season, but Barnes is the known quantity, already making his presence known as a freshman, he'll be in a much more prominent role this season. If he can get consistent pressure, it'll make the rest of the defense more dynamic and make Butler's transition to the DC a lot easier.