USC fans have surely looked at crosstown rival UCLA at times this season and thought, "If only the Trojans had made a coordinator change as impactful as what the Bruins did in hiring D'Anton Lynn over the offseason ..."

And surely, UCLA fans have in turn thought, "If only the Bruins had any stability at the QB position whatsoever ..."

The latest rivalry showdown between the schools Saturday in the Coliseum will be a clash of polar opposite football teams.

USC ranks third nationally in scoring at 43.8 points per game, led by star quarterback Caleb Williams, who's impact is made all the more important each week by the Trojans' dismal defense, which ranks 123rd out of 130 FBS teams in giving up 446.5 yards per game and 120th in scoring defense (34.64 PPG).

UCLA, meanwhile, is led by its defense -- one that ranks ninth nationally in points allowed (16.4 PPG) and 10th in total defense (289.9 YPG) -- but has been consistently undermined by its offense and merry-go-round at quarterback. The Bruins rank 69th in scoring at 26.4 PPG overall, but they have scored just 17 points combined the last two games and have only hit 30 points once since mid-September.

"It’s hard to time it out sometimes where it all clicks at the same time," USC coach Lincoln Riley said, talking about the Bruins but just as fitting an observation on his own program. "... Defensively, they’ve done a really nice job. They’ve got a tremendous front seven, those guys have stayed healthy, they’ve been consistent and they’ve really driven that defense and they’ve got some play out of the back end as well and just been really, really consistent.

"It shows you when you get that right group together and you can get a little bit of momentum like they have defensively, you can really push it and ride it on any side of the ball."

The Trojans will assuredly be riding their offense Saturday in what could be Williams' final game as a Trojan, though he has made no formal declaration of the sort yet.

But even though it's the final regular-season game of a mostly lost season and what's left of this defensive staff isn't likely to return with the eventual hiring of a new coordinator, Riley has said several times this week that he wants to -- and expects to -- see a real response by that unit Saturday.

"I expect us to take a major step forward this weekend, I do. Plain and simple. I expect it, [interim co-DCs Brian Odom and Shaun Nua], our defensive staff expect it, our players expect it. We said at the beginning of the week, we have to make Week 2 of this group and this staff setup, we've got to make this an advantage for us. We've got to [take advantage of] the fact that guys at the front of the room are different, a few of the things we've done schematically are different," Riley said. "We've changed a few things in terms of how we've practiced -- nothing drastic -- but all of that is less new now. ...

"That's been the expectation of every single person in the room, and we kind of laid those out Monday with the guys and they've accepted it. It certainly feels tighter, it certainly feels cleaner throughout the week, less new, but we've got to go put it on the field Saturday."

It's crazy think how much has changed for these programs when they met a year ago -- a dramatic 48-45 Trojans win with both programs seemingly to be on a clear ascent.

Now, coach Chip Kelly is on the hot seat suddenly at UCLA (6-4, 3-4 Pac-12), while Riley looks to be starting his rebuilding project with the Trojans (7-4, 5-3) anew.

The collective disappointment of this season is the one thing the two programs share in common.

Rivalry games rarely disappoint, though, and even with lesser stakes this should be a compelling clash between the Bruins and Trojans on Saturday in the Coliseum.

Let's break down the matchup and scout UCLA further ...

Who | UCLA (6-4, 3-4 Pac-12) at USC (7-4, 5-3)

Where | Coliseum

When | 12:30 p.m. PT Saturday

TV | ABC

Radio | KABC 790 AM

Spread | USC is a 5-point favorite

Over/under | 64

Series history | USC leads the all-time series 52-33-7 (not excluding any vacated wins). UCLA has won just 6 of the last 24 meetings dating back to 1999.

Last offseason, Chip Kelly signed a contract extension through 2027, but he's back on the hot seat with speculation mounting that he could be let go after this season. In his sixth year with the Bruins, he has a career record of 33-33 while peaking at 9-4 last season.

The Bruins started 3-0, lost a competitive 14-7 game at Utah and won the next week over Washington State with another impressive defensive performance to move to 4-1. But it's been tough going since then with their only wins coming against lowly Stanford and reeling Colorado as they've dropped to 6-4.

UCLA has had no stability at quarterback all season, initially through indecision and later dictated by injuries. Both Ethan Garbers and five-star freshman Dante Moore were injured in the loss to Arizona two weeks ago, which thrust Kent State transfer Collin Schlee into action in the loss to Arizona State. Either Garbers or Moore should be available Saturday, but neither has been overly successful this season. Garbers has passed for 786 yards, 6 TDs and 3 INTs, while Moore has thrown for 1,344 yards, 10 TDs and 7 INT.

Neither has been able to fully take advantage of what looked like a huge transfer addition at wide receiver in J.Michael Sturdivant, who was one of the best wideouts in the Pac-12 last season at Cal but has just 28 catches for 428 yards and 3 TDs this fall. Former Trojan Kyle Ford also has not had the kind of impact many might have envisioned, with just 13 catches for 152 yards. The Bruins' top pass-catcher has been slot weapon Logan Loya (40-502-4).

At running back, Ball State transfer Carson Steele has rushed for 745 yards (5.2 YPC) and 6 TDs while T.J. Harden has run for 533 yards (5.1 YPC) and 5 TDs.

Much of the Bruins' offensive issues start up front, as they lost three starting offensive linemen from last year and didn't bring in any impact transfers to fill those voids. They've given up 33 sacks this season.

UCLA totaled just 243 yards vs. Utah, 271 vs. Arizona and 300 vs. Arizona State, but it has fared better against worse defenses, putting up 503 on Stanford, 487 vs. Colorado, 471 against Washington State and a very respectable 453 vs. Oregon State.

Not much was made of it when UCLA plucked NFL position coach D'Anton Lynn, who had never coached in college, to be its defensive coordinator, but the move has paid huge dividends for the Bruins, as he's turned around a UCLA defense that ranked 87th last season (403.8 YPG) and now ranks 10th in giving up just 289.9 YPG. The Bruins have held seven of their 10 opponents under 300 yards -- including Utah (219), Washington State (216), Colorado (242) and Arizona State (250).

They've been particularly dominant against the run, ranking first nationally in holding opponents to 70.8 rushing yards per game.

It starts up front for UCLA with a stout defensive line led by DT and former Trojan Jay Toia, and edge rushers Laiatu Latu and brothers Gabriel and Grayson Murphy. Latu ranks fourth nationally with 11 sacks and lead all FBS players with 18.5 TFL while the Murphy brothers have combined for 9 sacks and 18.5 TFL.

At linebacker, Darius Muasau leads the team with 59 tackles (including 4 sacks and 8 TFL), while Cal transfer Oluwafemi Oladejo has been a steady contributor with 41 tackles.

Nickel Alex Johnson, a sixth-year senior, leads the team with 4 interceptions while cornerback Jaylin Davies has a pick and a team-high 5 pass breakups.

UCLA has held seven of its 10 opponents under 100 rushing yards, including some extremely dominant totals -- Coastal Carolina (56), San Diego State (63), NC Central (90), Washington State (12), Stanford (24), Colorado (25), Arizona State (74).

We could go a number of ways here, but how about the fact that UCLA has only allowed one 300-yard passer all season -- Arizona's Noah Fifita, 300 yards.

Given that the Trojans can't count on their defense, even in a more favorable matchup, and that UCLA has been so dominant against the run and the Trojans are quick to abandon the ground game, this one could rest of the shoulders of Caleb Williams -- fittingly, in possibly his last college game.

Williams vs. UCLA's pass rush and secondary is the most intriguing matchup to us.