After Lincoln Riley's final game as Oklahoma's head coach in 2021, the loss to rival Oklahoma State, he was asked about rumors linking him to the vacant LSU head coaching job.

"Let me stop you right there. I’m not going to be the next coach at LSU," Riley said, later reiterating that he never even took a call about that job.

The next day, Riley was the head coach at USC, Brian Kelly would get the Tigers job and now the two go head-to-head Sunday to start their third seasons at the respective schools as the No. 23-ranked Trojans take on No. 13 LSU in Las Vegas.

“Ton of respect for him. He’s obviously done a great job everywhere he’s been, he’s been a really good program-builder, he’s had success at different levels. I think he’s done a great job. Somebody I’ve admired for a long time," Riley said this week of Kelly. "We talked about a job when I was at East Carolina. We had a meeting about a job when he was at Notre Dame. That was kind of my first real experience with him, and I was super impressed at the time. It was cool, just being a young coach at that point and getting a chance to meet him, spend some time with him, so that was really a positive experience.

"And then, yeah, our paths have crossed at times kind of here and there over the different years. We’ve had some mutual friends, some people that have either worked with myself and with Brian that we know very well. ... I [feel[ like I had a pretty good idea of who he is and obviously a tremendous coach.”

Both head coaches have a lot riding on this 2024 season -- especially Riley and the Trojans, who are looking to show that the 8-5 finish last year was merely a hiccup and that new defensive coordinator D'Anton Lynn and his staff can deliver a quick fix for what was one of the worst defenses in college football last year.

They'll get every chance to make a statement Sunday in going up against one of the best offensive lines in college football in a LSU group that has combined for 98 career starts, led by left tackle and preseason All-America pick Will Campbell (26 starts), followed by right guard Miles Frazier (25), right tackle Emery Jones (24) and left guard Garrett Dellinger (23). Redshirt freshman C DJ Chester is expected to make his first career start in the game.

And Campbell has already thrown down the gauntlet in stating this week.

"We're going to run the ball. That's not something we're hiding or trying to keep quiet. I'm telling everybody right now, we are going to run the football. So you can take what you want with that," he said.

To be fair, he was talking about the LSU season in general -- not a matchup-specific plan for the Trojans.

But this may be the best test USC's rebuilt defensive front -- leaning heavily on transfers Gavin Meyer (Wyoming) and Nate Clifton (Vanderbilt), along with junior Bear Alexander -- gets all season and it comes right out of the gate.

"There's a lot of [areas of the team] that I'm that I'm excited to see. I mean I think our D-line, you know, certainly is probably there at the top," Riley said. "We've made obviously a lot of changes there. I mean pretty much every single possible way you can change it, we've changed it, from how we practice, certainly the size, the nutrition factor that's been well documented, obviously the weight and the strength that we've put on these guys and that we've brought in, certainly how we are playing, not just call-wise but from a technique standpoint is very different as well.

"And so, yeah, to see us get a chance to go put that on display is important. And I think of any of the changes that have happened, that position room, it's been the most extreme. And so I think that naturally for me, that's the one that I'm most excited to see."

But the same could just as easily be said for a USC linebacker group hoping that the arrival of Oregon State transfer Easton Mascarenas-Arnold has a reverberating effect in bringing out the best from returning starter Mason Cobb. Or a rebuilt secondary relying on transfer additions Kamari Ramsey (UCLA) and Akili Arnold (Oregon State) at safety and Greedy Vance Jr. (Florida State) at nickel, among others, with Jaylin Smith stepping into a new role at cornerback and veteran Jacobe Covington looking to finally establish himself at the other corner.

One game won't provide a full evaluation on the Trojans' defensive rebuild, but it will certainly start the assessment in a big way.

LSU finished last season first nationally in scoring (45.5 points per game) and total offense (543.5 yards per game), and while they are also replacing a Heisman Trophy-winning quarterback in Jayden Daniels along with their top two receivers (also just like USC) and offensive coordinator, the Tigers should be a formidable challenge nonetheless.

"We’re prepared. We’ve known what the challenge is going to be since I got the job here," Lynn said. "We’ve been preparing not just for LSU, but just for the entire season and what we have to be prepared for."

Internally, there seems to be genuine confidence in what the defense has built behind the scenes, but the players know that nobody is going to forget what happened last season until they provide a real reason.

Sunday in the national spotlight is a big opportunity to do just that.

"I enjoy the questions. I enjoy the talk. I enjoy all of it," defensive end Jamil Muhammad said. "... I mean, yeah, spring game and stuff like that, but until you have a real chance to show what you've been working on and how much better you've gotten, what you did and what everybody saw is going to be on their minds until you change it. So obviously our focus isn't on changing everybody else's mind. However, our focus is on getting better and fixing those things that we know we have to be better at. ... I can't wait to see us go at it."

Let's take a closer look at the matchup ...

When | 4:30 p.m. PT, Sunday

Where | Allegiant Stadium, Las Vegas

TV | ABC, with Rece Davis, Kirk Herbstreit and Holly Rowe

Stream | WatchESPN.com

Radio | ESPN LA 710AM Radio, starting at 2:30 p.m. PT with Pete Arbogast, Shaun Cody, Cody Kessler, Su’a Cravens, Jordan Moore and Jason Schwartz

Betting line | LSU -4, over/under 64.5

Series history | This is the third meeting all-time between the programs with USC winning on the road in the 1979 and LSU winning in the Coliseum in 1984.

Shared history | Of course, USC and LSU shared the 2003 national championship with the Tigers winning the BCS crown with a 21-14 win over Oklahoma while the Trojans claimed the AP title after going 12-1 with a win over Michigan in the Rose Bowl. While the teams didn’t’ meet on the field that year, they were both invited to the White House in March of 2004 to celebrate the national title with President George Bush. The 2003 season marked the final time two teams shared the national championship in football.

Preseason rank: No. 13

2023 record: 10-3, 6-2 SEC

Head coach: Brian Kelly, 3rd season (20-7 at LSU; 283-103-2 career)

Overview: Kelly and the Tigers also hit the reset button on defense after last season, replacing former defensive coordinator Matt House with Blake Baker, who held the same position at Missouri last season.

Meanwhile, Kelly lost his offensive coordinator Mike Denbrock to Notre Dame and promoted QBs coach Joe Sloan and WRs coach Cortez Hankton to co-OCs with Sloan taking over the play-calling.

The Tigers made the SEC championship game in Kelly's first season but fell short last year and have finished outside the top-10 in the national rankings each of his first two seasons, putting a little extra pressure on him to take the next step with the program this year.

LSU loses reigning Heisman Trophy winner Jayden Daniels at quarterback and should look a lot different offensively in turning things over to redshirt junior Garrett Nussmeier, who is more of a pro-style QB than the dynamic dual-threat playmaker Daniels was for the Tigers.

Nussmeier and USC QB Miller Moss were both in the 2021 recruiting class -- ranked one spot apart as the No. 7 and No. 8 pro-style QB prospects that year -- and have both waited their turn while finally making their first career start last bowl season.

Like Moss, Nussmeier seized his opportunity while passing for 395 yards, 3 TDs and 1 INT in a win over Wisconsin in the ReliaQuest Bowl.

But there isn't a ton of tape on the QB from which to scout.

"He has a very strong arm. He can make every pass on the field. He doesn't have a lot of playing experience, but when he is out there you can't tell. He plays with a lot of poise, he handles himself well in the pocket, he extends plays well, he's always looking to keep the play alive throwing the ball downfield, so he presents a lot of issues," USC defensive coordinator D'Anton Lynn said.

"Anytime you're going in and it's really his first season starting, obviously, you just make best with information that you have."

The Tigers are also replacing top wideouts Malik Nabers (89 catches for 1,569 yards and 14 TDs last season) and Brian Thomas Jr. (68-1,177-17) -- both now set for major roles in the NFL this season -- with redshirt senior Kyren Lacy (30-558-7) and redshirt junior Chris Hilton Jr. (13-225-2) the top returning wideouts. LSU also brought in Liberty transfer CJ Daniels (55-1,067-10). Hilton is listed as questionable with a bone bruise after getting in limited work in practice this week. If he can't go, redshirt freshman Kyle Parker would be in line for a bigger role. Tight end Mason Taylor was third on the team in receiving last year with 36 catches for 348 yards and a TD.

But as left tackle Will Campbell noted, the identity of this LSU offense is expected to be its rushing attack behind that aforementioned veteran offensive line.

While Daniels was the Tigers' leading rusher by a wide margin last season. Sophomore Kaleb Jackson (31 carries for 165 yards and 4 TDs last season) and fifth-year senior Josh Williams (55-284-5) are expected to lead the backfield. Williams led LSU in its bowl game with 51 rushing yards on 12 carries.

"They're big, physical backs, they have a big offensive line and they have big tight ends, so they present a lot of issues in the run game," Lynn said.

The big name on LSU's defense is junior linebacker Harold Perkins, who is a preseason first-team AP All-America pick. He has 26 tackles for loss, 13 sacks, 7 forced fumbles, 9 pass breakups and 2 interceptions in 27 career games.

Fellow linebacker Greg Penn is also a big-time player for the Tigers, ranking second on the team last season with 89 tackles along with 6.5 TFLs, 4 sacks and 2 INTs.

While the Tigers were one of the worst pass defenses in the country last year (see chart), they do return a good bit of experience at the defensive back spots. Senior safety Major Burns led the team last year with 93 tackles along with 3 TFLs, 1 INT and 3 PBUs and redshirt junior safety Sage Ryan (42 tackles, 4.5 TFLs, 5 PBUs) played mostly cornerback last year but has moved all around the secondary. Sophomore cornerback Ashton Stamps (23 tackles, 2 PBUs) got a lot of action as a freshman while sophomore cornerback Javien Toviano played regularly as well and drew a start late in the season.

Up front, senior defensive end Sai'vion Jones (33 tackles, 2.5 sacks last season) is a returning starter while redshirt senior defensive tackle Jacobian Guillory made one start last year and looks poised to anchor the middle of the defensive line now.

Ultimately, though, the Trojans can only glean so much from watching LSU's film from last season as the Tigers should look different under new coordinator Blake Baker, who led a Missouri defense that featured an aggressive pass rush last season (tied for 11th nationally with 39 sacks).

"It is what it is," Lincoln Riley said. "There's parts of it that, yeah, sometimes you wish you were sitting there watching the people you're going to play do exactly what they're going to do or at least run their system. But then the flip side of it is, it's their first game in a lot of areas too. It's going to be ours in some, so yeah, you've got to make the most of it, you've got to be ready to adjust in first games. Because even if it's the same system people are going to have made adjustments, they're going to change and evolve throughout the year."

Running back Kaleb Jackson handled the bulk of LSU's kick returns last season, averaging 24.9 yards per return with a long of 60 vs. Auburn, but junior Mississippi State transfer Zavion Thomas could get a look at both punt and kick return duties. He had a 63-yard punt return touchdown vs. Georgia in 2022 and a 94-yard kickoff return touchdown vs. Texas A&M last year.

Damian Ramos returns as the placekicker after going 12 of 15 on field goals last season, while redshirt junior Peyton Todd takes over as the punter.