Mike Elston has been here before.
Back in the spring of 2010 - with the arrival of the Brian Kelly regime - the inherited defense was in disrepair following a No. 86 ranking in total defense during the final season under Charlie Weis. Opponents from the 2009 season averaged 170 yards rushing per game against the Irish.
It was Elston who was entrusted with re-establishing a defensive front that could hold the point of attack. He had a couple of anchors - nose guard Ian Williams and defensive end Ethan Johnson - around which to build.
But Kapron Lewis-Moore, the emotional leader of one of the best defenses in Irish history two years later, was still a pup. Louis Nix was preserving a year of eligibility, and Stephon Tuitt was still plying his trade on the prep gridirons in north-central Georgia.
"We had these issues when we first got here with guys (not) playing aggressively," said Elston, who is in his fifth year at Notre Dame. "There was some experience there, but Kappy was a young guy at the time learning how to play aggressively.
"So when I look at our group today, yeah, we're young. There are guys that have not played defensive line before that are in the two-deep. It's just a matter of reps and them understanding how they play. There's a long way to go."
Teaching a bunch of youngsters how to play with a level of aggression that befits a program that played for a national championship 15 months ago is more than half the battle. Players adapt to new schemes fairly quickly. It starts with physicality up front while also making a transition in style of play with the shift to a shoot-the-gap approach.
"It's a much more aggressive attack for a defensive lineman," Elston said. "You have to be aggressive in anything you do, so that's probably not a fair assessment. But we've got to be more aggressive at the line of scrimmage coming off the ball.
"A year ago, most of the time, we were waiting on a guy to move, and then we were key-stepping with them and trying to work a knock-back. But now we're coming on, we're taking it across the line of scrimmage and attacking them."
According to Elston, the three players who have adapted to the new style of play the best have been interior defensive linemen Sheldon Day and Jarron Jones, the former a veteran of two seasons and the latter a ray of hope over the final month of the 2013 campaign, and to a lesser extent, Romeo Okwara. (Editor's note: For more on all of Notre Dame's defensive personnel along the defensive line, look for an upcoming story with Mike Elston.)
Elston's last experience coaching a one-gap front came back in his days with Kelly at Central Michigan (2004-06). As a graduate assistant at his alma mater, Michigan, in 1999-2000, the Wolverines ran a similar system.
"We're being multiple in the spring, so there's a lot of carryover, but there's also a lot to learn," Elston said. "There's been a lot of resetting some things that they haven't done in a long time. But it's been exciting. They're enjoying it. We're pushing them hard, but there's a lot for them to learn."
Not surprisingly, the defensive linemen feel as if the chains of bondage have been broken. Instead of reacting to the movement of the offensive linemen - running interference for the linebackers to come up and make a play - it's on the defensive linemen's shoulders to penetrate gaps and make a few plays of their own.
This fall, they'll have to do it without four of the anchors that helped hold opponents to 14 points or less in 15 of the last 26 games of the Bob Diaco-led defense.
"We're replacing three key guys," Elston said. "Kona Schwenke was a critical component (along with Nix and Tuitt). He added a lot of depth at different positions and played a ton of football. So we're not just losing two guys, we're losing three, along with Prince Shembo, who was a great addition in there when we went to third down and pass rush.
"So we've got a lot of key guys that we've got to replace. The frustration is just repetitive mistakes."
Regardless of the scheme, it all starts with trying to establish a greater degree of aggressiveness.
"We're making a lot of progress with them understanding how they have to play," Elston said. "We've got to continue to work on aggressiveness and toughness and grit. We still need to be a more physical group.
"Consistency is big. That's always going to be the case. We have a sign in the defensive line meeting room (that says): 'Consistency is the truest measure of performance.' If you can do it one day and you can't do it the next day, you're not going to be a good performer. We've got to come out every single day and perform.
"You're always going to try to be aggressive no matter what package is run. You've got guys that are going to be naturally aggressive and you've got guys that need to grow that aggressiveness."
With just five practices remaining, Elston wants to exit the spring feeling better about his unit than he does at the two-thirds mark.
"I want everybody's game to move forward," Elston said. "At the end of 15 practices, I want them to be ready and amped up for the fall. I don't want to have to try to fix a bunch of technical things like using their hands and the way their feet move coming out of their stance. I'd really like to clean that up, and I'd like to see all the guys improve their aggressiveness.
"We're getting better at technique, they're understanding the package and we're having a lot of fun. It's been a fun spring. The guys enjoy the package. They're getting better. We're hard on them. We're grinding them pretty good. We need to."