Notre Dame players celebrate after beating Indiana 27-17 in the first round of the College Football Playoff, Friday, Dec. 20, 2024, in South Bend, Ind. (AP Photo/Darron Cummings)

SOUTH BEND, Ind. (AP) — Notre Dame’s defense set a dominating tone early in its College Football Playoff opener against Indiana. The Fighting Irish stuffed the highest-scoring team in the CFP field for a 14-3 halftime lead, but then Notre Dame suffered a gut punch.

Defensive lineman Rylie Mills sacked Indiana quarterback Kurtis Rourke on the first play of the second half, and had to be helped off the field with a knee injury.

Heading into its CFP quarterfinal game against second-seeded Georgia, the Fighting Irish are determined to make sure the setback doesn’t turn into a letdown.

The Fighting Irish (12-1) finished with a 27-17 victory against Indiana, giving up two touchdowns in the final two minutes after building a 27-3 lead. Now Notre Dame has to replace Mills, its sack leader this season, for the game against Georgia (11-2). Kickoff for the Sugar Bowl is scheduled for Wednesday at the Superdome in New Orleans.

“So we feel badly for (Mills), but at the same time … we just don’t flinch,” Notre Dame defensive coordinator Al Golden said. “We move forward. It’s time for somebody else to have an opportunity, and I know they’ll be ready.”

After a shocking 16-14 loss to Northern Illinois in the second game of the season, Notre Dame’s defense led the charge for an 11-game winning streak that lifted the Fighting Irish when the offense struggled to find its footing. And the defense has done it while being forced to replace a series of key players.

Mills was a force on Notre Dame’s defense, which is ranked first in the nation in team passing efficiency defense (96.94), first in turnovers gained (29), first in defensive touchdowns (6) and third in scoring defense (13.8).

Notre Dame’s defense punished opponents this season despite losing four starters to season-ending injuries — linemen Mills, Jordan Botelho and Boubacar Traore (all knee injuries), and cornerback Benjamin Morrison (hip). Freshman linebacker Kyngstonn Viliamu-Asa (knee injury) hasn’t played since he was hurt in the Army game. Jason Onye, a defensive tackle, hasn’t played since the fifth game because of a personal issue.

Seventh-seeded Notre Dame needs the defense to come up big once more against powerful Georgia and a quarterback it knows little about.

Notre Dame head coach Marcus Freeman is counting on Gabe Rubio and Donovan Hinish to step up and take turns filling in for Mills.

“You don’t prepare them in a week,” Freeman said of players stepping up to replace starters. “They’ve been preparing every single day all season long.

“That’s why every rep you do in a practice matters and is evaluated,” Freeman said. “You don’t know when that rep is going to be thrust against Georgia. You have to prepare in a way in practice that you’re improving, but you’re ready if your number is called.”

Howard Cross III, a defensive lineman who has teamed up with Mills to be the leaders of an imposing defensive front, had just returned to the Fighting Irish lineup for the playoffs after missing three games with an ankle injury.

“It was heartbreaking,” Cross said of seeing Mills go down.

Cross said it’s been an unusual season with the injuries, but facing a 14th game, everybody is dealing with pain.

“The whole thing is no one’s healthy, no matter what position you are, no matter what you’re doing,” Cross said. “Your hamstring could be sore, like somebody’s hurt in some way, shape or form. Some worse than others.

“It is kind of a testament to the mental toughness of this team,” Cross said of the defense always being ready. “The whole thing for us is like, God forbid you go down, the next guy up has to know exactly what they’re doing. We are expecting the next guy up to have the same or better production than the guy that’s starting right now.”

Notre Dame’s defense faces the challenge of replacing Mills and getting ready for a Georgia offense led by Gunner Stockton, who replaces injured starter Carson Beck.

“You evaluate, obviously, schematically, what they’ve done all season,” Freeman said of preparing a different look from the Bulldogs. “Then you have a separate tape of what Stockton, the new quarterback, has done. I think we have 80-something plays of him playing quarterback. He can run their offense. He does some things a little bit differently. He can extend plays with his legs. He’s a good athlete.

“The thing I probably notice more than anything, in watching those 80 plays, is he’s an ultra-competitive individual,” Freeman said of Stockton. “You can just tell by the way he celebrates, by the way he goes and finishes plays. He’s a competitor. I don’t see it being tremendously different than what they’ve done all season, but we’ll prepare for anything.”

Georgia head coach Kirby Smart doesn’t anticipate a diminished Notre Dame defense despite the personnel issues.

“They play great defense and great pass rush,” Smart said. “They’re physical up front. They affect the pass rush with how hard they play, and they got really good defensive backs. They play man-to-man. They get up on you, put their hands on you.”