Notre Dame’s offense enters the College Football Playoff ranked 26th in S&P+. The Irish ranked in the exact same spot in 2017, when they went 9-3 before winning the Citrus Bowl. This offense ranked 36th in 2016, when they went 4-8, but ranked seventh in 2015.

Overall, the 2018 Irish offense hasn’t been any better than it’d been the last several years, though things improved once Ian Book took the reins at QB.

On defense, Notre Dame is No. 4 in S&P+, up from the 20s and 30s for the last three years. They had bad defenses under Brian VanGorder and improved slightly under Mike Elko in 2017, but Elko left for Texas A&M after one year in South Bend.

New coordinator Clark Lea, who’d joined in ‘17 as linebackers coach, has taken advantage of having one of the most experienced units in the country.

All 11 defensive starters are juniors, seniors, or grad students. Five backups are upperclassmen.

The defense is a collection of guys who were supposed to be studs and panned out — seven starters were long ago blue-chip recruits — and guys who weren’t but did anyway. Junior corner Julian Love is a 5’11 ex-three-star who became a finalist for the Jim Thorpe Award, while junior safety Alohi Gilman transferred from Navy, where he’d committed as an unrated recruit.

The Irish do a solid job keeping offenses off schedule. They’re 17th in Marginal Efficiency allowed, a measure of how often opponents’ plays are successful.

But they’re No. 3 in Marginal Explosiveness, a measure of how successful those plays are. Even when teams get the bare minimum yardage to keep themselves from falling behind (which they usually don’t), the Irish are great at preventing more.

This shows up in more conventional stats, too. The Irish have given up 35 plays of 20-plus yards (eighth fewest nationally), 12 of 30-plus (fourth), five of 40-plus (tied for fourth), two of 50-plus (tied for eighth), and zero of 60-plus, which only 10 teams can say. They’ve played a lot of drab offenses, but it’s still impressive to limit them so consistently.

Head coach Brian Kelly said this in the offseason (emphasis ours):

“For example, last year we would do up-downs after practice if we had some mistakes. We don’t do that anymore. There’s a sense of peer accountability that Clark likes to build within the unit that helps build pride in how they do their job. They’re gonna teach the same system, but how they get to that end is a little bit different based upon their philosophies.”

In other words: all that experience didn’t have to learn a new system.

The most common alignment for ND’s defense is a 4-2-5 with corners in off coverage.

The Irish aligned like this against Syracuse, which is built to stretch a defense horizontally and vertically ...

... but also against Michigan, which is content to pound between the tackles:

Notre Dame allowing only the bare minimum yardage is by design. The Irish dare you to dink-and-dunk, sustain drives, and avoid a mistake over the course of 10 or more plays. That’s something a lot of college teams can’t do.

It also forces offensive coordinators to be disciplined, because the Irish are a hard team to take shots against.

Let’s take this third-and-6 against Michigan. Notre Dame shows blitz but backs out of it and only rushes four. But the Irish still get a sack:

Pretend for a second the Irish do blitz all six guys, as they showed pre-snap. UM’s Grant Perry (the second receiver at the bottom) creates separation at the top of his route right at the sticks. The throwing lane would be open if the protection could hold and the throw could come in rhythm. Instead, Notre Dame drops linebacker Te’von Coney back into coverage, and he floats into the throwing lane.

This is where Patterson wants to go with the ball:

Maybe the QB could try to lead the receiver toward the sideline, but that doesn’t work here, because the Irish run stunts are on his ass.

ND gets home in a sound way: rushing four and dropping seven into coverage.

Here, the Irish show a six-man blitz and back off, with two linemen going into coverage:

Here, they show six and bring five, with a linebacker holding back to make sure a mobile quarterback can’t take off on third-and-short.

The anchor is tackle Jerry Tillery, but he has a lot of help. His teammates’ ability to get push makes the whole thing work.

Notre Dame loves to use these disguises and stunts on third down, rather than heavy blitzing. That fits with a bend-but-don’t-break philosophy: create chaos, but don’t sell out.

Zone defense might be “soft”, but it certainly isn’t passive. These dudes suck all that space up aggressively. They’re asked to make a lot of open-field tackles. If someone catches that ball underneath, that’s fine, because he’ll be down soon after. This is another reason why you don’t see a ton of big plays allowed.

A few players make ND go in pass coverage, and they all have really good ball skills.

Coney’s got great ability to break on the ball and make a play:

Drue Tranquill is the epitome of the modern nickel hybrid, with blinding speed and a mean streak.

Love is elite as an off corner. He closes space with the best of ‘em. That’s key here ...

... and here:

To help, ND has two safeties with exceptional ball skills. Here, Jalen Elliott reads Syracuse QB Eric Dungey’s eyes the whole way, then breaks on the ball to get an interception:

His fellow safety, Gilman, does the same thing later in the same game. He knows where the ball is going, flips his hips, and goes to get it.

The average drive against Notre Dame goes 26.7 yards. That’s good, but not incredible. Why’s Notre Dame so good, then?

It’s not because of turnovers; the Irish are tied for 42nd in takeaways. And it’s not because of field position. The average drive against Notre Dame starts at the opposition’s 28.2-yard line, putting the Irish defense 38th in starting spot.

Aside from big-play prevention, stingy goal-line defense is the key. Opposing offenses get Scoring Opportunities (inside the Notre Dame 40) on 40 percent of their drives, a pretty normal rate. But they’re only coming away with 3.3 points on those trips.

That has the Irish at No. 4 in points allowed per Scoring Opportunity.

The closer an offense gets to the goal line, the stingier the Irish get, even beyond what most defenses do.

When teams get to the doorstep, they usually stall out.

The funny thing: the Irish still give you all that space when they’re not literally on the goal line.

That works because they close quickly on the ball. This, for instance, forced a field goal against Michigan:

When a team gets down to the goal line, the Irish can hold the point of attack:

And their open-field tackling shows up when a miss would be back-breaking:

They don’t get many turnovers. They are 42nd in Havoc Rate, a stat that rolls in interceptions, forced fumbles, sacks, tackles for loss, and pass breakups. They don’t have a megastar.

But everyone’s good, and on the occasions this defense slips up, it almost always gets its act together in time.

This style is about to meet its stiffest test. USC made the Irish look like they were in quicksand for a half, but Clemson’s ability to stretch a defense with both scheme and talent will be new. The Tigers might be able to break this great defense, but Notre Dame won’t make it easy.