At some point during the Trojans' stark second-half-of-the-season swan dive last fall, head coach Lincoln Riley fully relented in accepting that major changes were needed on the defensive side of the ball.

Changes to the staff, changes to the defensive scheme, changes to the broader vision for building the unit, changes to the goals of the offseason strength and conditioning program, changes to ... everything, basically.

Give Riley credit for ultimately owning all of that.

He had steadfastly maintained throughout last offseason and leading up to the fall that he had the right man for the job at defensive coordinator in Alex Grinch. He stubbornly pushed back on the mounting questions about the defense through the first part of the schedule, as the Trojans got off to a clearly flawed 6-0 start, telling critics that they were looking at it with "untrained" eyes and not seeing the progress he saw.

But eventually Riley's eyes came into focus as well -- accepting that there was no progress coming, that the critics indeed had it right -- and everything he's said and done since then should provide even his doubters reason to believe that he's learned valuable lessons these last two seasons.

"We’re going to do everything that we can in this program to accelerate the process of us playing great defense at USC," Riley said in December, setting a new tone for his program. "And whatever it takes to get that done from a development standpoint, from a staffing standpoint, from the way that we practice, everything here is going to be done with a defensive mind first. ... Again, the edge here is always going to go to what’s best for our defense."

RELATED: USC spring roster revealed -- notes, new jersey numbers and weight changes

While he was rebuilding 80 percent of that defensive staff -- with only Shaun Nua remaining, sliding over from defensive line coach to defensive ends coach -- Riley was also noticeably on the road visiting defensive prospects. Six of the final seven recruits to commit to USC in the 2024 recruiting class, all after the end of the regular season, were on the defensive side. Seven of the 11 transfers USC signed over the offseason were defensive players.

Meanwhile, that new staff Riley built started with poaching defensive coordinator D'Anton Lynn from crosstown rival UCLA after a highly-successful one-season stint there that made him a burgeoning rising star in the sport. In the most surprising move of all, Riley and Lynn then lured a sitting head coach away from one of the most successful FCS programs in the land as Matt Entz left his enviable post at North Dakota State to come coach the linebackers here. They also hired Eric Henderson (who looks poised to make a dramatic impact on USC's defensive line recruiting) away from a comfortable NFL job as DL coach with the Los Angeles Rams, and an experienced former defensive coordinator in Doug Belk to coach the secondary.

"I think we have a staff right now that takes a backseat to no one, period. I believe no one in football -- not just college football," Riley said last month.

In addition to his actions, though, Riley's words further made clear his commitment to doing a complete 180 from the Grinch era. He's made rather candid comments about how he prioritized hiring a defensive coordinator "who had displayed and showed the ability to really adapt well to the personnel, a coach that schematically was strong and schematically had the ability and wasn't so tied into one thing."

Hmmm.

Riley also emphasized that from now on USC needed to recruit and develop bigger defensive linemen and that the new DC had to be "somebody that wanted to play bigger on the defensive front," whereas many criticized Grinch for prioritizing speed over size up front.

"I think certainly just throughout the second half of the season feeling like we had to really make some real drastic changes there in terms of the body types to be able to play the way we wanted to play," Riley said. "And some of that was knowing obviously after we made the change [at defensive coordinator] that we were going to be going in a different direction in terms of schematics and how we use those guys, so it just kind of fit together."

From those notable admissions on the roots of the defensive failures the last two years to the sweeping changes that followed, there's nothing more Riley could have done these last four months to fully untether himself from the Grinch era and inspire fresh optimism after that 1-5 finish to the 2023 regular season.

The next step starts Tuesday, as the Trojans take the field for the first of 15 spring practices.

It's wild that after losing a Heisman Trophy-winning quarterback, who is the prevailing expected No. 1 pick in the upcoming NFL draft, the major storyline this spring is not about finding his replacement.

There is intrigue there with UNLV QB transfer Jayden Maiava coming in, don't get us wrong, but redshirt junior Miller Moss sure looks like the guy for the job and he won't be able to further answer any questions about his readiness for the role until the season starts.

USC will also look almost entirely different at running back, is launching a full-on youth movement at receiver and tight end and has some major questions along the offensive line, but the spotlight this spring is undeniably affixed squarely on this remodeled, work-in-progress Trojans defense.

To delve deeper into that and other storylines, here are 24 thoughts on the 2024 Trojans as they open spring practice Tuesday afternoon ...

1. QB Jayden Maiava

We're on record here that we believe Miller Moss has a firm grip on the starting quarterback job, at least entering the season. I mean, did you watch the Holiday Bowl?! Six touchdowns, plenty of poise, heaping praise from his teammates who believe he deserves his shot -- it all adds up. But that doesn't diminish the intrigue that Maiava brings to the roster. He passed for 3,085 yards, 17 touchdowns and 10 interceptions as a redshirt freshman at UNLV and is a capable runner. If USC has to turn to him this season for any reason, he'd bring a lot to the table, and it will be exciting to get a first glimpse of him this spring (to the limited extent that media are permitted to see anything).

2. LB Easton Mascarenas-Arnold

As we'll expound on in a bit, the linebacker situation should be totally fluid until this staff has a chance to make its own evaluations on everybody. But the fact that the coaches prioritized bringing in help at LB and that they landed a guy who was one of the better players at the position in the Pac-12 last year sure makes us think that Mascarenas-Arnold (who transferred in from Oregon State with his brother, safety Akili Arnold) has the inside track to one of the two starting spots.

3. S Kamari Ramsey/CB John Humphrey

These two go together as they both have a year of experience starting for D'Anton Lynn at UCLA. They clearly believed enough in Lynn's impact as a DC to follow him across town. It's not just that connection that lands them on this list, though. USC lost a ton from its secondary and Ramsey and Humphrey fill key needs with proven talent and have as good a chance of landing starting roles as anyone in this crowded defensive backfield.

4. DL Nate Clifton

The first transfer to hop on board this offseason, Clifton posted 5.5 sacks and 7.5 tackles for loss at Vanderbilt last season. He played both on the edge and on the interior of the defensive line for the Commodores at 6-foot-5, 280 pounds. USC is thinnest on the interior and the hope would be that Clifton can be an impactful rotation piece at defensive tackle.

5. RB Jo'Quavious "Woody" Marks

USC has hit it big with transfer running backs since Lincoln Riley has been in charge -- Travis Dye and MarShawn Lloyd were game-changers and Austin Jones had some big moments as well. With Lloyd, Jones and veteran Darwin Barlow departing the program, USC wanted a proven veteran to add to its talented collection of young running backs. In comes Marks, who tallied 3,108 combined rushing/receiving yards and 27 touchdowns the last four years at Mississippi State. He averaged 4.6 yards per carry for his career in the SEC and should play a significant role in the offense this year. That said, don't sleep on the young talent at the position ...