Let's jump back to early October. In the afterglow of Ben Koyack's miraculous 4th-and-11 touchdown catch, the Irish won a 17-14 slugfest against Stanford in what felt like a freezing monsoon.
While all Irish fans could talk about was Koyack's tightrope-walking along the chalk in the corner of the end zone, Brian VanGorder's defense was the real story.
The Irish held Stanford to just 205 yards of total offense. The Cardinal ground game that had Irish fans so worried? It gained just 47 yards. It was the fifth straight game where Notre Dame held its opponents to 17 points or less.
VanGorder, with his NFL schemes and overperforming personnel, received a tip of the cap from frustrated Stanford head coach David Shaw after the game.
"I think they’ve got an outstanding defensive coordinator. He mixes it up,” Shaw said after the loss. "Our quarterback got hit a lot today. Give them a lot of credit for their scheme."
All of that seems so far away.
From that point on, things have gone wrong. Very wrong. Notre Dame has only won two games since that victory over Stanford. And the defense has been a large part of the issue.
In the Irish's two victories, they gave up 82 points. North Carolina scored 43 with its hyper-speed offense catching the Irish defense completely out of sorts. And Navy's triple-option attack forced VanGorder and head coach Brian Kelly to simply hold on for dear life, with the Irish scoring 21 fourth-quarter points to pull away from the Midshipmen.
The easy thing to do is simply to blame VanGorder. After going viral for his fist-pumping exploits after shutting out Michigan for the first time in school history, the first-year coordinator now sits in quarantine—held to blame for the slide that's seen the Irish give up 30 or more points in six straight games.
But it's not all on VanGorder. As we look at the free fall of the Irish defense as it prepares to face USC's star-studded offense, let's take a look at the key factors that have contributed to the collapse.
Any analysis that doesn't peg injuries as the primary cause of this free fall isn't being fair to the parties involved.
Notre Dame's defense has been decimated by injuries. They've hit both key personnel and the limited depth that was being counted on to play important reserve minutes.
The first domino to fall was middle linebacker Joe Schmidt, who was injured against Navy. Schmidt's absence has been felt both on the field and off—both before the snap and during the action.
Against the run, the Irish have struggled greatly without Schmidt in the middle of the defense. As freshman Nyles Morgan has learned on the fly, the defense has given up big-chunk runs at an alarming rate.
In the 13 quarters without Schmidt, the Irish have given up 31 runs of 10 yards or more. They allowed just 25 in the seven-plus games Schmidt played behind Sheldon Day and Jarron Jones.
Speaking of Day and Jones? They've been lost for the rest of the season, with Kelly hoping that Day will return for the bowl game.
The coaches never had a true contingency plan for the defensive tackle position in absence of the duo, and it's forced Kelly and VanGorder to try and replace two players they knew going into the season really weren't replaceable.
Freshman Daniel Cage played well behind them but has missed time with his own knee injury. That's forced fifth-year afterthought Justin Utupo into the lineup and pulled the redshirt off of freshman Jay Hayes.
The rest of the injuries have chipped away at the foundation of the unit. Middle linebacker Jarrett Grace has been unable to play after last season's catastrophic leg injury that broke in four places. Tony Springmann retired before the season started after failing to get past a knee injury.
Safety Drue Tranquill is the latest hard-luck injury at a position that's seen Austin Collinsworth missing for most of the year and Nicky Baratti go down with another season-ending shoulder injury. Throw in Cody Riggs, whose foot injury has robbed the Irish of their most versatile cornerback.
Simply put, every level of the defense has been crushed.
It's worth reminding people that the Irish defense was hit hard during fall camp when the suspensions of starters KeiVarae Russell and Ishaq Williams took two of the most experienced players off the field for the season.
Throw in reserves Kendall Moore and Eilar Hardy (who is now back with the team), and that's four veterans who were likely to contribute in some form.
Russell's loss was the most difficult to take. Expecting to perform at an All-American level this season, Russell was anticipating a hard decision at the end of the year: head to the NFL or return for his senior season and his degree.
All of that was derailed after an academic issue in summer school put Notre Dame's football program in the headlines for the second straight season for the wrong reasons. Russell will return for his senior season—after spending his two-semester suspension away from South Bend.
The loss of Wiliams was also a huge blow. While sophomore Isaac Rochell and freshmen Andrew Trumbetti and Grant Blankenship have played well, having a physically mature senior like Williams to set the edge would've given the Irish someone with actual playing experience to line up alongside Day and Jones.
The Irish made it through the first five weeks of the season looking like they had skated through the suspensions unscathed. But the depth issues that were just beneath the surface caught the Irish, especially once injuries began piling up.
Put simply, the offenses that Notre Dame started the season against just weren't very good. Only Rice has ended up as a top-75 offense. Stanford is 81st in total offense, Syracuse is 112th, Purdue is 113th and Michigan is 117th.
Just as injuries and depth issues began piling up, so did the better offenses. Only Louisville and Northwestern rank outside the top 75 in total offense. They combined to score 74 points against the Irish. Arizona State, Navy, North Carolina, Florida State and USC all average between 452 and 441 yards per game—each in the top 40 of total offense.
Entering Saturday's finale against USC, nine freshmen are on the final defensive depth chart of the regular season. Seven sophomores join them—a total of 16 out of 22 in a defensive two-deep in their first or second year of eligibility.
That's a lot of kids seeing their first chunk of significant playing time as the Irish desperately search for answers on defense and their long-awaited eighth win of the season. That experience will serve this team well in the future.
But with a rivalry game against USC set for Saturday, nobody is willing to look that far ahead.
So Kelly and VanGorder will be asked to find answers. Even if they're out of places to look.
*Unless otherwise noted, all quotes obtained firsthand.