CHICAGO — At times, it wasn't aesthetically pleasing. It certainly wasn't perfect. But if 12 games and 10 wins have told us anything about the 2015 Northwestern Wildcats, it's that that's exactly how they like it. Ugly. Scrappy. Gritty... Beautiful.

To the 2015 Northwestern Wildcats, ugly, scrappy and gritty are synonymous with beautiful. And, well, that's exactly how their coach likes it too.

"We know who we are," Pat Fitzgerald said repeatedly after topping off a remarkable season with a 24-14 win over Illinois at Soldier Field. "And we've embraced that here through Big Ten play. And some games it's been better than others, but we know exactly who we are, and we've stuck to that formula."

That formula wasn't always the cleanest. It certainly wasn't Saturday. The Wildcats didn't dominate. They rarely have in 2015. As has become customary, Northwestern's offense sputtered, especially after halftime.

But as has also become customary, Northwestern's defense led it to victory. And in doing so one final time, it firmly nailed down this team's place in Wildcat football lore. It permanently stamped its identity into the record books and into the minds of fans with a win emblematic of what and who this team is.

This team... is Pat Fitzgerald's Northwestern.

It took 10 years. It took flirtations with various schemes and philosophies. It of course took struggle and failure. But in 2015, for the first time, from early September through late November, we have seen Pat Fitzgerald's Northwestern.

How do we know? The evidence is everywhere.

First and foremost, it's on the field. Fitzgerald's imprint is all over this team. His connection to the romance of the "old days" — to tough-guy football, to grind-it-out, gut-it-out slugfests — manifests itself in this defense's play. Its relentlessness — a word former NU head coach Gary Barnett drove home in 1995 — is a product of Fitzgerald's attitude, one he's implanted in the psyches of his players.

"[Fitz] knows what it looks like, being a two-time All-American, and playing on great defenses," defensive end Deonte Gibson said Saturday. "He knows what it looks like to be a great defense... He understands defense is a dirty, gritty, grimy position to play, and you have to understand that."

The Fitzgerald disposition is contagious too. It hasn't just affected Gibson, or his classmates. Perhaps the greatest ode to this defense is that there isn't one single lasting image of it. There's a long list of them. There's Anthony Walker knifing into the backfield from Fitzgerald's old position and clobbering opposing running backs. There's Gibson overpowering opposing offensive tackles. There's Dean Lowry doing just about everything. There's Matt Harris giving quarterbacks hell. There's Nick VanHoose running receivers' routes before they themselves can. There's Godwin Igwebuike darting sideline to sideline, corralling even the fastest of scatbacks.

Talent helps, of course, and this is the most talented and deepest unit Fitzgerald has had yet. That too is part of Fitzgerald's Northwestern. So is defensive coordinator Mike Hankwitz. "How Hank is not a semifinalist for the Broyles Award..." Fitzgerald wondered aloud. "Can you guys write him in? Because that's a joke. I don't know who's watching."

But there's something more to it, as there often is in football. The evidence of Fitzgerald's Northwestern is also in the pride in the head coach's voice. He acknowledges his team's weaknesses. He knows it must improve, most notably on the offensive side of the ball. "I'd love to put up the Baylor numbers," he said Saturday. "I'd love to put up some of the numbers that these other teams are [putting up] offensively. But they can't shake a stick at our defense."

In a way, the offensive struggles are part of the team's identity, just as much as the stout defense is.

"We're a Chicago football team," Fitzgerald says. "We're kind of old school — '95, neck roll, four yards and a cloud of dust. To a lot of people, that's boring. I could care less what they think. I call it winning."

Win is exactly what Northwestern has done. It has done so in a fashion that is perhaps unsustainable. But for now, who cares. It has done so 10 times in 12 tries. It's NU's first 10-win regular season since 1995, when Fitzgerald himself wore that neck roll and stood at the heart of a previous iteration of "Pat Fitzgerald's Northwestern," the one he likely hopes this one will become.

And it's well on its way to doing so. "Obviously," Fitzgerald said postgame, "our defense is pretty special."

The first glimpse into the new version of Fitzgerald's Northwestern came 14 months ago. The Wildcats went to Happy Valley and dominated Penn State, keeping the Nittany Lions out of the end zone in a 27-6 victory. After the game, our Josh Rosenblat wrote the following:

Redshirt freshman Anthony Walker proved that Northwestern has the young athletes to shut down a powerful Big Ten offense. But don't forget about true freshman Xavier Washington's huge sack and forced fumble that also proved it. Or sophomore Matthew Harris' should-have-been strip and score. Or sophomore Greg Kuhar's penetration on that big fourth-and-one stop. Or sophomore Ifeadi Odenigbo's constant pressure. Or redshirt freshman Godwin Igwebuike's consistent play as a sub at safety. Those are the young guys that proved that the defense does have the athletes to allow Northwestern to win despite its offense, not because of it. It's clear, now a quarter of the way through the season, that this Northwestern team is not built in the mold of the Randy Walker/Kevin Wilson spread teams, and that's okay. Northwestern has the defense to win games. On Saturday, there were no facades. There were no disguises. Northwestern, for the first time in years, seemed like Pat Fitzgerald's Northwestern.

Northwestern no longer merely seems like Fitzgerald's Northwestern. After a season of defensive dominance, it is.

"This is the best defense I've played on in my entire life," Gibson said Saturday.

It's also the best — and in a figurative sense the first — of Pat Fitzgerald's tenure at Northwestern.