In the second installment of an eight-part spring practice series, Notre Dame's defensive line will be the specimen being analyzed under the microscope.
It's a unit that has evolved into a dominant, line-of-scrimmage-controlling bunch that head coach Brian Kelly envisioned possessing when he accepted the job in December 2009. And with two returning starters as well as a wealth of quality depth, the Irish front line will be considered among the nation's best.
The defensive line is the key ingredient in defensive coordinator Bob Diaco's 3-4 scheme, as its ability to move and control the line allows him to implement a variety of exotic blitz packages and pass coverages.
And the position most responsible for controlling the line, nose guard, is the first position I'll discuss in this week's spring preview.
The Irish were blessed by the return of incumbent starter Louis Nix III, who decided that his NFL aspirations could wait one more season.
The 6'3", 326-pound behemoth is able to dictate the action at the line of scrimmage through his ability to draw double-teams as well as effectively plug the A-gaps (either side of the offensive center).
This means that run-first teams such as Michigan State will prefer to assign two blockers to Nix, creating opportunities for Irish pass-rushing specialists to plow their way into the backfield through open lanes.
What makes Nix such a special player and rare talent is his burst off the line that catches slower, less athletic offensive linemen off-guard.
The Jacksonville, Fla. native has made significant strides during his career at Notre Dame, developing from an overweight freshman to a potential All-America candidate as a redshirt junior.
When Nix needs a breather, senior Kona Schwenke is readily available off the bench.
A 6'4", 290-pound Hawaiian, Schwenke boasts a tenacity and high motor that are oftentimes able to offset a lack of athleticism against more explosive offensive linemen.
Incoming freshman Eddie Vanderdoes, a 6'3", 310-pound defensive tackle who was billed as a 5-star talent by Rivals.com, appears to be a natural fit at nose guard in a 3-4 scheme, though the possibility exists that he could see time at defensive end in 2013.
Depth will be the critical factor that sets it apart, as very few teams in the country boast three nose guards capable of being effective pieces in a 3-4 scheme.
The alpha male of the defensive line, Stephon Tuitt, returns for his third season as a starting defensive end at Notre Dame and is already being projected as a top-10 pick in the 2014 NFL Draft.
Tuitt, a 6'6", 303-pound monster, led the Irish in sacks in 2012, dragging opposing quarterbacks down 11 times.
A surefire All-American, Tuitt provides a fearsome presence that caught the eye of Rivals.com, which compared Tuitt to two-time Pro Bowler Shaun Ellis, who played for both the New York Jets and New England Patriots during his 12-year NFL career.
Starting opposite Tuitt will likely be sophomore Sheldon Day, a former 4-star prospect (per Rivals) in the 2012 class out of Warren Central High School in Indianapolis.
A smaller player than Tuitt—checking in at 6'2" and 286 pounds—Day tied for fourth on the team in sacks a season ago with two, adding to his 3.5 tackles for loss.
However, the sign of an elite defensive line isn't simply possessing outstanding starters. Depth becomes a significant advantage as the season wears on.
The Irish will boast plenty of depth at defensive end, with Tony Springmann, Chase Hounshell, Isaac Rochell and Jarron Jones competing for minutes as backups.