A month ago, it seemed unthinkable.

Dave Aranda’s departure to LSU was supposed to be a setback for the Badgers. The defensive coordinator who brought his own, high-pressure defensive scheme to Madison would undoubtedly be missed. He was the guy behind Wisconsin’s top-scoring defense in 2015.

This wasn’t a team with household names. Sure, guys like Joe Schobert and Vince Biegel became stars in 2015, but they were considered system players by many. It wasn’t a unit loaded with NFL talent like Alabama or Ohio State. Without Aranda, nobody knew what was in store for the Wisconsin defense in 2016. Aranda’s magic formula was supposed to be working wonders down in the Bayou leading a College Football Playoff contender.

Aranda did plant the seeds for a defense that’s growing into a playoff-caliber group before our eyes, it’s just not happening where everyone expected.

The Wisconsin defense hasn’t taken a step back without their former defensive coordinator. If anything, the Badgers have taken a step forward with Justin Wilcox.

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Somehow, Wisconsin’s defense is out-performing last year’s group. And more impressively, the Badgers are doing it against better competition.

One could’ve probably figured that out from watching Saturday’s game at No. 8 Michigan State. Wisconsin forced four turnovers and pressured MSU quarterback Tyler O’Connor on 51 percent of his drop backs, according to Pro Football Focus. The Badgers held a Mark Dantonio-coached team scoreless for the second time this century.

Despite some gaudy numbers last year, Wisconsin’s 2015 defense never had that good of a performance against a top-25 team.

But before we break down the quality of Wisconsin’s opponent, take a look at the defensive numbers Wisconsin put up this year compared to last year on a per game basis (regular season only).

PER GAME STATS 2015 UW DEFENSE 2016 UW DEFENSE
Points allowed 13.1 (No. 1 in FBS) 11.8
First downs allowed 14 14
Offensive touchdowns allowed 1.60 1.25
Total Yards 267 277
Points allowed per possession 0.82 (No. 1 in FBS) 0.66
Percentage of scoring possessions 16% 15%
Red-zone chances allowed 1.83 1.75
Opponents held under 100 yds. rushing 58% 75%
Third-down conversion percentage 31% 24%
Turnovers forced 1.67 2.25

Ok, that’s a lot to digest. Here are a couple other things to consider with this year’s Wisconsin defense.

The 11.8 points per game allowed by the 2016 group doesn’t take away an interception return and a special teams return allowed. Get rid of those and the Badgers are allowing 8.25 points and 0.75 touchdowns per game.

In other words, Wisconsin has been even better than the numbers suggest. And oddly enough, Georgia State was the only offense that scored multiple touchdowns against the Badgers so far.

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Last year, the 2015 defense might not have gotten much respect nationally for a few reasons.

Eventual-national champion Alabama ran all over that group in a prime-time season-opening game. Wisconsin also racked up its impressive defensive numbers against a favorable conference schedule. After the season opener, the Badgers didn’t face another ranked squad until the home finale against Northwestern. They lost that game, and the defense wasn’t rewarded with a win for arguably its best performance of the year against Iowa.

RELATED: What gauntlet schedule? Wisconsin is a legitimate playoff contender

This year is already a completely different story in that regard. Wisconsin has wins over two top-10 teams in the same season for the first time in over 50 years. Both of those victories were fueled by defensive dominance.

As good as last year’s group was, it never had anywhere near that kind of success vs. top 25 teams. That, more than anything, is what gives this year’s group the early edge.

AVERAGES VS. TOP-25 TEAMS 2015 UW DEFENSE 2016 UW DEFENSE
Points allowed 23 6.5
Rushing yards 151 101
Passing yards 182 191
Total yards 332 291
Third-down conversions 36% 21%
Turnovers forced 0.33 3.5

Keep in mind that neither of Wisconsin’s top-10 wins were at Camp Randall Stadium. And while 2016 LSU has proven not to be as dominant as 2015 Alabama, many would argue that Leonard Fournette was a bigger challenge than Heisman Trophy-winner Derrick Henry was.

So how has this year’s unit risen to the occasion? It’s really the same culture that Aranda established with his 3-4 scheme. Pressure, pressure, pressure and then some more pressure.

RELATED: Week 4 B1G Grades

It might surprise some to know that Wisconsin was only 64th in the country with 2.08 sacks per game in the 2015 regular season. This year, the Badgers are 32nd in FBS with 2.75 sacks per contest.

A lot of that is because of the emergence T.J. Watt, who picked up 2.5 sacks and a B1G Defensive Player of the Week honor for his performance at Michigan State. Watt and Biegel combined for a whopping 20 quarterback pressures that day. Along with Jack Cichy and T.J. Edwards, the Badger linebackers are still the heart and soul of this unit.

Aranda’s speciality in Madison was putting blitzing linebackers in the right spots. When Cichy recorded his sack-trick against USC in the Holiday Bowl, he got to Cody Kessler virtually untouched all three times. Even Cichy gave the credit to Aranda for his superstar moment.

After Saturday’s dominance, it déjà vu. Except instead of Aranda getting credit for putting guys in the right spots on key blitzes, it was Wilcox.

There was a play early in the second quarter in which Edwards and Watt overloaded the left side and blitzed. Edwards got to O’Connor and Sojourn Shelton did the rest:

What was responsible for that? Wilcox tweaked the Badgers’ blitz packages during the week, which obviously confused the Michigan State front. That was a manageable third down that Wilcox’s call turned into a game-changing play for the Badgers.

You could go back and find a bunch of times in which the exact sequence played out under Aranda. Th 2015 team doesn’t win 10 games without the job he did. The 2016 team doesn’t get off to a 4-0 start without Aranda, either.

RELATED: Badgers, quarterbacks highlight B1G Players of the Week

Veterans like Biegel and Cichy will be the first to tell you about the impact he made on the program. Aranda established a culture of relentless defensive pursuit. It wasn’t Wilcox’s job to come into Madison and reinvent the wheel. He saw what worked, and now his adjustments are paying major dividends for the Badgers during this gauntlet of a start.

It’s odd to think that the Badgers are heading into October with arguably the most impressive résumé in the country while LSU already fired Les Miles and offensive coordinator Cam Cameron. Aranda left Madison for what he — and most — believed would be greener pastures. Even though that hasn’t proven to be true, there aren’t any bitter feelings in the locker room surrounding his departure.

Why would there be?

“If Dave Aranda called me up right now, I’d ask him how he was doing, obviously,” Biegel said. “And I’d let him know that the Wisconsin defense is on the right pace.”

Yeah, you can say that again.