The Karlen File: Experience, Energy, and Everything in Between
Notre Dame football has always thrived on its rich traditions, hard-nosed defense, and players who embody the Fighting Irish spirit. In 2025, few names better represent those qualities than linebacker Nolan Karlen. A name perhaps not as widely recognized outside of South Bend yet, Karlen has quietly carved out a reputation as a critical piece in Notre Dame’s defensive identity—a player whose experience, energy, and relentless presence make him one of the most important figures in the Irish locker room.
At 6-foot-3 and just over 230 pounds, Karlen is built like the prototypical modern linebacker—athletic enough to cover tight ends downfield, stout enough to hold up against the run, and instinctual enough to diagnose plays before the ball is even snapped. But what sets Karlen apart isn’t just his physical makeup; it’s the mental and emotional intangibles that have made him a cornerstone of Notre Dame’s defense.
Entering the 2025 season, Karlen is no longer the young, raw recruit trying to crack the two-deep. He’s a seasoned veteran, one of the team’s most experienced defenders, and a leader whose presence is felt far beyond the stat sheet. After emerging in a rotation role early in his career, Karlen gradually earned the trust of the coaching staff through his consistency and intensity. By 2024, he was taking the majority of reps at inside linebacker, and his snap count skyrocketed as the year went on.
Now, as a senior, Karlen is embracing his final chapter with the Irish. What makes him unique is the way he channels his experience into every rep, every meeting, every moment. For younger players, he’s a model of how to prepare and how to play. For coaches, he’s a reliable extension of the staff on the field. And for opponents, he’s the kind of guy who seems to pop up on every play, even if he wasn’t supposed to be involved.
What you immediately notice about Karlen when watching film isn’t just the tackles or the pressures—it’s the motor. Every snap is played with urgency. He chases down screen passes, redirects tight ends across the middle, and blitzes with a kind of fury that disrupts quarterbacks even when he doesn’t get home. That kind of energy is infectious, and it’s a big reason why the Irish defense, under coordinator Al Golden, has become increasingly aggressive and confident.
Energy alone, though, doesn’t make a great linebacker. It’s Karlen’s ability to pair that tenacity with cerebral play that truly elevates his game. He’s a film junkie, someone who prides himself on understanding not just his own responsibilities, but everyone else’s. Ask anyone in the program, and they’ll tell you that Karlen is often the first guy in the film room and the last to leave. He doesn’t just want to know what the offense is doing—he wants to know why they’re doing it, when they’re likely to do it, and how to beat it.
It’s that level of preparation that makes Karlen such a trusted communicator on the field. He’s constantly adjusting alignments, calling out pre-snap tendencies, and barking reminders to the secondary and the front seven. The Irish defense thrives on communication and discipline, and Karlen is the glue that keeps it all together when chaos hits. Coaches will often say that the best linebackers are like quarterbacks for the defense, and Karlen has become exactly that.
That wasn’t always the case. Early in his career, Karlen struggled with the speed of the college game. Like many young defenders, he was sometimes a step late or a tick hesitant. But rather than get discouraged, Karlen doubled down on preparation and development. He added muscle without sacrificing quickness, studied more film, and soaked up every coaching point he could. That work ethic has paid off in the form of both individual success and team-wide respect.
It’s not just his teammates who have taken notice. NFL scouts have begun circling Karlen’s name in their notebooks—not necessarily as a first-round pick, but as a high-floor, smart, tough player who can contribute on special teams immediately and eventually push for a starting role. He’s the type of player who elevates a locker room and shortens the learning curve for everyone around him.
But ask Karlen himself, and he’s not thinking about the draft just yet. His focus remains squarely on winning games at Notre Dame and being the best leader he can be. That unselfish mentality has endeared him to the fan base and coaches alike. He talks often about leaving the program better than he found it, and his actions back up that mission.
Off the field, Karlen is equally admired. He’s a consistent presence at community events and team outreach programs, often volunteering his time without fanfare. He’s earned academic honors and is pursuing a degree that speaks to his desire to impact lives beyond football. Those who know him best describe him as humble, focused, and grounded—exactly the kind of player Notre Dame fans love to root for.
And it’s not just about personality. There’s no denying Karlen’s on-field production. In 2024, he racked up over 80 tackles, 9 tackles for loss, 3 sacks, and a handful of pass breakups. But even those numbers don’t fully capture his impact. He’s the guy who makes the stop on 3rd-and-2. He’s the guy who diagnoses a screen and blows it up before it develops. He’s the guy who doesn’t come off the field when the game is on the line.
Heading into the 2025 season, Notre Dame’s defense is expected to be one of the best in the country, and Karlen is a massive reason why. With a mix of returning talent and promising young depth, the Irish will lean on veterans like Karlen to set the tone, especially in high-leverage situations. Whether it’s opening weekend under the lights or a cold November showdown with playoff implications, you can bet No. 45 will be in the middle of it all.
For a program that has long prided itself on producing elite linebackers—from Manti Te’o to Jaylon Smith to Jeremiah Owusu-Koramoah—Karlen is carrying the torch in his own way. He may not be the most physically gifted linebacker to wear the gold helmet, but his all-around game, leadership, and infectious energy make him every bit as vital to the Irish cause.
In many ways, Nolan Karlen is the type of player who defines successful programs. He may never win a Heisman or generate weekly highlight reels, but he wins in the margins. He executes the game plan, lifts his teammates, and plays with heart. And those things, as every coach will tell you, win football games.
As Notre Dame eyes a College Football Playoff berth in 2025, the team will face plenty of challenges—tough road environments, elite quarterbacks, and high-stakes moments. But with Nolan Karlen at the center of its defense, the Irish know they have a steadying force who can meet those moments head-on. Whether it’s a goal-line stand, a third-down stop, or a crucial halftime adjustment, Karlen will be there, barking signals, flying to the ball, and leading with everything he’s got.
That’s what makes “The Karlen File” more than just a collection of tackles or accolades. It’s a story of experience, of energy, of a player who found his way through hard work and heart—and is now the soul of one of the most storied programs in college football.
