Jaylon Smith jokes that he's 19-going-on-30, the whirlwind of a rapid rise up the depth chart and standout rookie campaign giving way now to the burden of being a bedrock on a Notre Dame defense short on upperclassmen but not potential.

Then the realization that Smith has upward of three more years in an Irish uniform washes over him, and the 6-foot-2.5, 230-pounder can't help but sound as eager as all who anointed him a can't-miss talent upon his pledge not even two years ago.

"Taking it day by day, trying to get better," Smith said of balancing the conflicting emotions. "That's really just the motto, not only for me but for us as a unit. We have to count on each other and hold each other accountable. I feel like the way we all approach the game, and improve, we're going to do anything [we can] to make us better."

Change is upon the Notre Dame defense, which has a new coordinator and, as of right now, significantly different strengths from its last time around.

Brian VanGorder is in for Bob Diaco as defensive coordinator, the secondary has replaced the defensive line as the known quantity and Smith, last seen tallying 67 tackles in the months following his arrival to campus, is now being relied upon more than ever, ready to show that the promise displayed last season was just a sliver of what's to come.

The former five-star recruit has moved from the dog outside linebacker spot to a position he describes as "Sam linebacker-slash-Mike," an integral piece to a defense that he says is now "definitely a 4-3."

"We don't want offenses to know where he is," head coach Brian Kelly said. "We're going to play him in a number of different positions. He could be inside, outside -- but we're moving him all over the place."

One of just two defensive returnees to start all 13 games last season (along with KeiVarae Russell), Smith's biggest challenge is expanding his football IQ, mastering not only his new position but also developing a better awareness of the responsibilities of the 10 others around him.

"That's always been a goal, that's how I view things," he said. "I'm wanting to potentially be the best and to be able to lead, and I think this year I'm going to get that chance, to take the next step up, of being more vocal in the locker room and being around the defense and learning the defense."

For all of his talent, Smith never forgets that his opportunity last summer to ascend from third to first on the depth chart came at the misfortune of Danny Spond, whose hemiplegic migraines forced the incumbent into early retirement during camp.

Smith was sure to make mention of his newest mentor at every turn last season, and the absence of Spond around the team this spring has not let Smith off the hook so easily.

From Spond to Smith, from Carlo Calabrese to Joe Schmidt, linebackers old and new have made sure to keep the conversation going through a group text message they started at the break of camp last August, back in Marion, Ind.

"Basically all the linebackers from last year," Smith said. "We speak almost every day, to be honest. Everyone's just seeing new information and those guys are old and moving on and actually getting ready to live life, and a couple of us are still here, grinding, just trying to have success for Notre Dame."

Still here -- sounding like anything but a guy going through his first college spring, and hoping to play like that's the case, too.

"I feel like I'm more experienced, I feel like I've been here forever," Smith said. "Time goes by so fast. I'm cherishing every moment of it."