The most compelling question about Notre Dame’s 4-2 start this season is what in the world has happened to its top-ranked defense from a year ago?
The Irish defense finished 2012 ranked No. 2 nationally in scoring, No. 11 against the run and No. 25 versus the pass. These numbers have taken a nose dive in 2013 with a No. 58 rank in scoring, a No. 29 rank against the run and a No. 87 rank versus the pass.
What it amounts to for Notre Dame is allowing opponents an additional 12.7 points per game. This is a huge deal for a team that, on average, beat opponents by 13 points last season.
So, what has happened to the Irish defense in 2013, a unit which gave up a whopping 76 points combined in its losses to Michigan and Oklahoma?
Is it a huge wave of personnel turnover, the departure of key leaders like linebacker Manti Te’o or instead, is the reason hidden somewhere in a pile of stats?
2012 vs. 2013
The first step in comparing the 2013 defense to its predecessor in 2012 is looking at the go-to guy at each position.
Given the drop in performance, it’s striking that the Irish only lost starters in four positions coming into this season. Of course, there have been swaps in terms of who is listed specifically where, but the net result is that the experience level is high.
Looking at the even bigger picture, according to Phil Steele’s calculations, Notre Dame returned 65 percent of its tackle earners in 2012 and 64.4 percent in 2013.
And remember that the guys coming back in 2012 had played for a unit ranked No. 24 in scoring in 2011 versus the 2013 returnees that had participated in the No. 2 national ranking.
All this adds up to a realistic expectation that the Irish defense would be comparable across the two seasons when in fact, it is not.
Since the attrition rates are low for the Irish on defense, it’s easy to argue that the loss of impact guys like Te’o and defensive end Kapron Lewis-Moore are the real cause of the setback.
Think of it this way: Last season Lewis-Moore contributed 40 tackles, eight-and-a-half tackles for a loss, six sacks and two forced fumbles last season while Te’o racked up 113 tackles, five-and-a-half tackles for a loss, one-and-a-half sacks and seven interceptions.
Both these guys leaving Notre Dame in 2013 makes a huge difference to the bottom line…right?
Well, Lewis-Moore and Te’o’s combined 153 tackles accounted for 18 percent of Notre Dame’s 873 tackles in 2012, while their 14 tackles for a loss accounted for 20 percent of the teams’ 69 tackles for a loss.
Furthermore, Lewis-Moore’s six sacks accounted for 18 percent of the team total of 33, while Te’o’s seven interceptions accounted for 44 percent of the team total of 16.
So, while the loss of the two was substantial, the departure of 20 percent of the statistical output shouldn’t signal a 56-slot free fall in scoring defense.
What's more difficult to gauge is how much impact the loss of Te'o had from a leadership standpoint. Te'o was the inspirational guy the rest of the unit followed, a journey that led to the national championship.
Is it possible that the Notre Dame defense played over its head in 2012 because of Te'o's emotional leadership?
Well, even though this could be part of the explanation, it still falls short of completely accounting for how the Irish defense morphed into a different—much less effective—unit during the offseason.
So, if it’s not a lack of experience or the departure of a key guy that's entirely to blame, what else has signaled the decline of defense at Notre Dame?
The answer starts with considering how a team can give up 12.7 more points per game but only allow 70 additional yards.
This means that the Irish are allowing almost two touchdowns extra per game to opponents, who miraculously score these points with only 70 more yards of offense.
How does this work?
Well, your defense gets put into a bad position by an offense that has already given the other team the ball seven times in 2013.
Included in that number is six interceptions in six games, which is just two shy of the eight total picks Notre Dame suffered through 13 full games last season.
So, there you have it.
Te'o is gone, and so are his services as a playmaker and an inspirational leader. But, also gone, is a quarterback that didn’t put his defense behind the eight ball.
Here’s the collateral damage thus far this season.
Of Rees’ six interceptions, five of them led directly to a touchdown by the opposing team. This amounts to 35 total points, or six points per game.
To put a finer point on it, Notre Dame’s defense was charged with an average of 11.66 additional points per game in the three contests that Rees threw interceptions in.
While that doesn’t provide a complete explanation for the decline in defense, it does serve up a heaping healthy of food for thought.