The Wildcats ranked last against the pass last season (230.4 ypg), a problem that will need fixing in order for NU to compete in the Legends Division this year. Two starting cornerbacks are gone from last season -- Jordan Mabin and Jeravin Matthews -- which makes those pass-coverage woes an even larger issue. So, who steps up to fill those gaps?
Redshirt freshman Daniel Jones struggled at times in 2011, but showed some promise and should improve enough during spring workouts to secure one of the starting jobs. Jones played in five games last season.
The other spot may belong to junior Demetrius Dugar, who battled Matthews in preseason camp for a starting spot in 2011. Dugar played well in limited action last season, including an impressive six-tackle performance against Iowa in which he also had an interception.
Other guys to keep an eye on are C.J. Bryant and Nick VanHoose, both of whom have made names for themselves in practice last year. Both of them will likely be on the two-deep, at minimum, and one of them could sneak into a starting role.
Who emerges as the starting safety next to Campbell?
Ibraheim Campbell went from the weakest link in the secondary to perhaps the best defender on the team during the 2011 season. The consensus Freshman All-American wound up leading Northwestern with 54 tackles last season and drew rave reviews from departed senior Brian Peters, who took Campbell under his wing.
The question is who will emerge to nail down the other safety spot. Hunter Bates and Jared Carpenter are the most experienced safeties on the roster, but both have battled injuries. Carpenter, who played in just eight games, won't be participating in spring drills. Bates, meanwhile, has good football instincts but struggled last season after suffering a broken leg in the 2011 TicketCity Bowl.
Sophomore Davion Fleming may push Bates and Carpenter in camp, but it's Jimmy Hall who could have a breakout year as the best athlete, next to Campbell, of the bunch.
Which young player(s) will emerge on the defensive line?
The Wildcats lost Jack DiNardo, Vince Browne and Kevin Watt, three cogs in the defensive line. This season, a new crop of young players have an opportunity to step up and help fix Northwestern's often leaky defense.
One guy that will be depended upon is Chance Carter, who earned significant playing time last season at defensive tackle. The athletic 6-foot-3, 270-pounder needs to improve his strength, but he's valuable because he could play either inside or outside on the line.
Another player who could be ready to make an impact on the field is Deonte Gibson. The redshirt freshman didn't play in 2011, but he has impressive burst off the line and could develop into a good third-down speed rusher.
Will this defense be able to rush the passer?
Without two of their top defensive ends from last season, the Cats may struggle to rush the passer again in 2012. Yet while those seniors will be missed, the Cats ranked last in the Big Ten in sacks in 2011, so really, they have no place to go but up.
Sophomore DE Scott had a breakout season and emerged as one of the Cats' best overall defenders in 2011. He may have been Northwestern's most consistent defensive linemen, showing good pass rushing skills and a great motor. Williams, a senior-to-be, was very effective at times last season. He was good enough to eventually supplant Vince Browne at right end, but he needs to work on becoming a consistent threat. At defensive tackle, likely starters Hampton and Arnfelt haven't show much pass rushing ability.
That means that young, unproven players like Gibson and Carter will have to step up and play a major role in NU's pass rush this season.
Northwestern does have some speed on the edge among its linebackers, however, so the Wildcats may have to resort to blitzing more often in 2012. Collin Ellis and Chi Chi Ariguzo are fast, athletic outside linebackers who could get to the quarterback when called upon.
Who will emerge as the leader on this side of the ball?
Peters was the leader of the defense last season, so someone will need to take that leadership role, lest the Cats' defensive struggles continue in 2012.
The frontrunner here is middle linebacker David Nwabuisi, who may be the only senior among the back seven for NU this year. He proved his worth last year, when he started at both middle and outside linebacker during the season. When he moved to weakside and Damien Proby to middle, the linebacker play improved. Nwabuisi is also an outgoing, vocal type of player who would be ideally suited to the role.
Another candidate is Campbell. Even though he is in just his second year in the program, he shows wisdom beyond his years and could step right into Peter's shoes.