In one forgettable night in South Bend, Indiana, all of USC's underlying issues came to the surface all at once Saturday.

The result was a 48-20 loss to rival Notre Dame, an 8-spot drop in the AP poll, a significant setback to the Trojans' College Football Playoff hopes and Caleb Williams' repeat Heisman campaign and a whole lot of uneasiness for a fan base now questioning exactly what this team is at this point.

As we do each week, we combed through the film to dive far deeper than the box score and stat sheet to find our 10 most significant takeaways from the Trojans' performance.

Believe it or not, there were some very encouraging changes schematically that could bode well moving forward, not to mention a defensive performance that deserves some recognition.

There was also plenty to critique and contemplate.

We break it all down in the weekly First-and-10 ...

It’s been clear for a number of games now that Caleb Williams hasn’t quite been playing up to the high standard he’s set for himself. Dating back to the matchup against Arizona State, Williams has been just a bit off, showing occasional lapses of accuracy and decision-making despite playing at a very high level otherwise. Though factors like offensive line play and play-calling have contributed, Williams’ issues have seemed like the primary factor in stripping away the machine-like ability of the Trojans offense to move the ball consistently.

Against ASU, Colorado and Arizona, that manifested in abruptly shortened drives and extended stretches where the offense struggled to stay on the field or score. Despite that, the bursts of brilliance that Williams provided were enough to pull the Trojans past the finish line in each of those contests. To be fair, Williams has often masked deficiencies around him with his brilliant play, to the point that we thanklessly expect him to do so every time. But that’s what comes with being the player he is.

It has to be assumed that this team’s ceiling is what Williams allows it to be; everything else around him can contribute to the Trojans’ success, but what’s required for it is for their star passer to excel. On Saturday, Williams played what was easily the worst game of his collegiate career, completing 23 of 37 attempts for 199 yards, 1 touchdown and 3 back-breaking interceptions. It’s those 3 interceptions that almost wholly swung the balance of this game -- twice placing the Notre Dame offense within the Trojans’ 15-yard line and giving the Irish the ball at midfield the other time. Mistakes like that are not just uncommon for Williams but exceedingly rare. In his first two seasons, he’d thrown just 4 and 5 picks respectively -- 3 in one game is wholly unprecedented for who he is as a player.

What’s most shocking is the nature of the interceptions, as not one of them was justifiable as a good-idea-gone-just-wrong. The first of them came just four plays into the game, as Williams inexplicably missed an easy throw to tight end Lake McRee over the middle, sailing it over his head to a waiting defender who proceeded to run it back to the red zone. That’s a throw I would expect him to hit 100/100 times -- even under pressure. That mistake gave the Irish an instant 7 points and a big swig of momentum to begin the game -- momentum the Trojans would never recover. Later, down just one touchdown in the second quarter, Williams made yet another confounding gaffe as he attempted a jump pass from within a collapsing pocket to a fully covered receiver. The ball was tipped at the line but never had much hope of being completed, and sure enough, it was once again picked off and ran back to the Trojans’ 1-yard line. What’s most frustrating is that Williams did have a wide open receiver waiting for him in the middle of the field -- uncharacteristically, he just never managed to find him. Though the Trojans defense had continued to hold strong, Williams’ mistake once again gave Notre Dame the football in prime scoring position, handing the Irish another 7 points.

Whatever hope remained of a comeback felt totally snuffed out on the subsequent drive, as Williams threw yet another inexplicable interception on a desperation heave from a heavily pressured scramble. The throw came on second-and-10; there was absolutely no reason for Williams to make a decision of that sort. The Irish scored a touchdown on the short field, and just like that, the Trojans went into the half facing a 18-point deficit.

Williams never really got it started through the rest of the game. He had spurts of good play and some excellent throws to show for it, but the Trojans offensive line crumbled further as the game went on. As pressure mounted, Williams seemed to lose his cool instead of showing his trademark poise from inside the pocket. He let his eyes get distracted, missed reads in his progressions and walked his way into sacks instead of getting the ball out quickly. Though the offensive line was undoubtedly bad, Williams wasted a handful of plays when he had a decent amount of time to throw by being indecisive with the football, as though he couldn’t bring himself to abandon his desire to extend the play in the face of circumstances that did not allow for it. As a result, the offense was never able to get going, allowing the Irish to pull away despite the USC defense’s mostly continued strong play.

Yes, the offensive line played very poorly and the receivers weren’t at their best, but I feel very confident in saying the Trojans would have won this game or stayed right in the thick of it to the end were it not for Williams’ three critical mistakes. Those three mistakes handed Notre Dame three touchdowns on a night when the USC defense only allowed the Irish to get into the end zone once on non-turnover drives. There are plenty of questions to be asked about the offense as a whole after this game, but no one factor was as responsible for this loss Williams was himself. This was a wildly uncharacteristic showing on his part, but the problems we saw had all been cropping up in bits and pieces through the past handful of games. Clearly, there’s something that Williams has going on that he needs to straighten out internally for this offense to be what it needs to be once again.

We know what he is capable of bringing to the table on a down-by-down basis -- it’s just a matter of understanding what’s keeping him from doing that right now and resolving it. This is the first game the Trojans have lost on his account since he came to USC, and if he can recenter himself, it should be the last.

There are two parties most responsible for the outcome of this game being what it was; one is Caleb Williams and the other is the USC offensive line. This was an awful performance by the unit, easily the worst of the Lincoln Riley Era at USC. For weeks, we’ve seen serious lapses of focus and communication on the line leading to bad snaps, penalties and blown assignments. This week however, those issues were compounded by the physical dominance of Notre Dame’s defensive front. Particularly on the interior, USC’s blockers struggled mightily to handle the Irish defensive line.

Those issues were clear to see in the run game, as USC noticeably struggled to generate any push off the line of scrimmage despite an evident desire to run the football. In pass protection, the Trojans appeared to be outmatched in a way that we hadn’t seen them be since Williams took over as signal caller. The linemen on the interior looked totally overwhelmed, especially when matched up with star defensive tackle Howard Cross. The trio of Emmanuel Pregnon, Justin Dedich and Jarrett Kingston gave up 7 pressures on the night (per PFF) -- by far their most of the year so far.

Pregnon had a very poor showing both as a pass and run blocker in this game, while Dedich posted the worst PFF pass-blocking grade of any USC starter this season at 46.1. For Dedich, this was his seventh straight game with a penalty. As a whole in that department, the group was once again poor as they totaled 4 flags drawn on the day. Those costly penalties put the team in multiple long-distance downs as they have all year; this time however, even Wiliams couldn’t save the day. Though the Trojans still might have gotten by with a normal game from their Heisman QB, it was the offensive line’s total subjugation that kept the USC offense from ever taking control of this contest. For the Trojans to win consistently, their offense needs to be one of the best in the country, and it simply cannot aspire to that unless the offensive line is much, much better than what we saw Saturday.

I’m not an expert on line play and I can’t say if the potential for that improvement remains at this point in the season. All I know is that things have to change if the Trojans are to have any shot at surviving the remainder of their schedule.

For weeks, many including myself have been calling for the Trojans to emphasize running the ball more to avoid the issues caused by a lack of ball-control on offense. Those issues have been persistent throughout Riley’s tenure with USC, as the pass-happy offensive scheme has led to short offensive drives and a persistent disadvantage in the time-of-possession column for the Trojans. That’s been particularly tough to manage in the second halves of games as the already-stretched defense wears out after extended time on the field, leading to unpleasant outcomes for USC.

Against Notre Dame, it became clear early on that Lincoln Riley had acknowledged the truth in those concerns and actively sought to address them. The Trojans ran the ball more in this first half than they had all season, tallying 21 carries through the first two quarters. Right from the jump, it was clear that USC was seeking a more balanced approach as it handed the ball off with regularity, even on down-and-distances that seemed to be exclusively marked for pass plays in the past. But again, the unfortunate problem was the offensive line had its worst day and found itself entirely throttled by the Irish defensive front. The line struggled badly to clear space for its runners, evidenced by the 73 yards generated on 19 carries overall by MarShawn Lloyd and Austin Jones.

The distribution of carries between the two backs was one of the more puzzling questions of the game to me, as I couldn’t understand why Jones saw significantly more action early on despite Lloyd’s clear advantages as a runner. Either way, neither back was really able to get going, aside from one brilliant 31-yard touchdown rush in which Lloyd found himself with acres of open field to maneuver through. Despite the functional difficulties caused by the mismatch between the Irish D-line and the Trojans’ O-line, the concerted incorporation of the run game into the USC offense bore noticeable fruit for the pacing of the game as a whole. For the first time all year, the Trojans were not dominated in the time of possession battle, instead out-possessing Notre Dame by nearly 10 minutes. Though some of that is borne of giving the Irish short fields off of turnovers, the reality is that the Trojans’ increased emphasis on the ground game ate away a considerable amount of clock. I don’t think it’s a coincidence that the USC defense played well all the way to the whistle in this game for the first time all year.

Though it’s a pity that the Trojans weren’t able to get much production out of the ground attack against Notre Dame, the fact that Riley was willing to adjust his strategy to lean into it further should be a point of relief. Keeping a more balanced approach going forward should do this team plenty of favors -- not the least of which being taking some weight off the shoulders of Caleb Williams and the passing game.

Much was made of the offensive play-calling following this game, as is to be expected when one of the nation’s most prolific offenses lays an egg in its most important game to date. For the most part, I didn’t feel as though bad-play calling was what lost this game for the Trojans.

Williams' three interceptions totally swung the game on their own merit, each of them the product of a bad mistake by the quarterback himself and no other. The offensive line clearly wasn’t ready to handle Notre Dame either, putting the team in a difficult position from which to operate a cohesive offensive strategy. As I’ve mentioned, I give Riley credit for the way he worked the run game into the gameplan, despite the fact that it never really got going. I’m sure that the intention was to work into some downfield play-action looks off of the establishment of the run early, but the play of the offensive line and the eventual game script likely rendered that moot. A good chunk of wasted plays in the passing game were a result of Williams not working his reads properly -- not necessarily because of the particular play design. With all of that said, there were a handful of areas in which the Trojans’ offensive decision-making or design appeared to hold them back.

The biggest of these is the lack of quick, rhythm passing plays in the USC offense. Though Riley’s offense does include a hefty share of quick passes, a majority of these plays are what I would call “cheese” plays -- manufactured looks that give the quarterback one easy choice to decide where to go to the football with a high degree of security. Though these plays are highly effective and do a lot for USC’s offense, they can be accounted for and met by a capable defense set on countering them. To beat pressure and get the ball out quickly on a reliable basis, you need true quick-game offense, where the quarterback’s reads are a bit more dynamic. To this point, the Trojans offense with Williams at the helm has never really needed much of this thanks to the strength of the protection and the success of the short-passing “cheese”. However, if the offensive line is going to be as shaky as it appears to be, the offense really would benefit from a different variety of quick-game concepts to work with.

Riley has plenty in his bag, as we saw at Oklahoma, and I’m certain the offense will start to lean on them more as they adapt to the circumstances.

On a separate note, my one deep, true irritation with this offense is its refusal to go under center, at least in short yardage situations. I simply can’t understand why the team has to run into defensive walls from deep in its own backfield over and over; there’s a reason almost every team in the NFL runs short yardage from under center. It cost the Trojans crucially in this game, as they failed to convert on a critical fourth-and-1 in scoring range early in the first quarter. At this point I’ve essentially given up hope on this changing any time soon, but it sure would be nice to see.