They arrived as top-10 quarterback prospects and left as top-10 NFL draft picks, yet they faced each other only once -- with Darnold winning a thriller in the Coliseum last season.
Their enormous talent was evident during their college careers, but the balance of power in the rivalry looks very similar after their departure to what it did upon their arrival. Under Darnold, USC won a Pac-12 title and a Rose Bowl as the Trojans reasserted themselves as a Pac-12 power. UCLA did little to shake its reputation as an underachieving program under Rosen, though that was through little fault of his own.
Call the 2018 season a reset in the rivalry. Two new quarterbacks and a new head coach present new possibilities in Los Angeles, but the question remains: Can UCLA learn to punch above its weight under new head coach Chip Kelly or will USC's edge in talent continue to keep the Trojans a step ahead in the Pac-12?
Kelly's return to college will go more smoothly if freshman quarterback Dorian Thompson-Robinson helps him immediately install the lightning-fast spread offense that powered him to 46 wins in four seasons at Oregon. Thompson-Robinson was ESPN's No. 2 dual-threat QB prospect in 2018, and his offense at Bishop Gorman High in Las Vegas was very similar to Kelly's Oregon offense.
"The offense is mostly catered toward me [more] than any other quarterback in that room," Thompson-Robinson told ESPN in May. "It's what I've been doing all my life. So it's really just up to how hard I work. If I go in there and lay an egg, it's definitely not gonna be my job. If I go in there and do me, I definitely think it's my job to lose."
With Ohio State's Tate Martell one year ahead of him, Thompson-Robinson did not start until his senior season at Bishop Gorman. Yet he was the nation's No. 34 prospect, throwing for 3,275 yards with 38 touchdowns and three interceptions. He also ran for 426 yards with seven more scores and spent the spring running track.
"If I go in there and lay an egg, it's definitely not gonna be my job. If I go in there and do me, I definitely think it's my job to lose."Dorian Thompson-Robinson
In his breakout performance in the Under Armour All-America Game in January, Thompson-Robinson looked the part of the fluid running quarterback Kelly loves, but he also showed impressive arm skills, throwing for 118 yards and a touchdown.
"He was a priority, to make sure we kept him committed," Kelly said of Thompson-Robinson on national signing day.
For Clay Helton at USC, there's more pressure for a fast quarterback rebuild. The success he had with Darnold helped restore some national credibility at USC, but it could be undone very quickly without the right quarterback, particularly in a Pac-12 South that has added Kelly and Kevin Sumlin at Arizona. The expectation of keeping the Trojans in contention will outweigh the 21 wins of Helton's first two seasons as full-time head coach.
Into the mix steps J.T. Daniels, the nation's No. 3 pocket passer, who took the unusual step by reclassifying and skipping his entire senior year of high school to enroll at USC this month. At 6-foot-2 and working to get to 210 pounds, Daniels looks the part, and all his film shows effortless passes from a guy who can make all the throws.
"I've started varsity in the No. 1 league in America for three years," Daniels told CBS Sports this spring. "I've seen enough of what the Trinity League has to offer. ... I don't think there's much more to learn in high school for me."
Daniels, the National Gatorade Player of the Year, started calling his own plays as a sophomore at national power Mater Dei in Santa Ana, California, about 35 miles from USC's campus. He broke former USC star and Mater Dei alum Matt Barkley's school record with 12,014 career passing yards and threw 152 touchdown passes to only 14 interceptions.
During a jam-packed spring with double the academic workload, Daniels made it to nearly every USC practice to take mental reps and study film with coaches. As quarterbacks Matt Fink and Jack Sears plodded through 15 up-and-down practices, Daniels was right there, his presence overshadowing their every throw.
"He attacks it, man. He gets after it," USC offensive coordinator Tee Martin said. "He's a gym rat when it comes to watching film. He's been doing installs since official visits. He's the first player I ever saw that on his official visit, all he wanted to do was football. Most guys want to hang out, want to see stuff. This guy's already past that. He's like, 'I want to get in the playbook and start learning.' When you see him and you start talking it with him, he's already speaking the language, he already knows it, he talks like he's been here for a couple of years."
Trojans coaches have gushed over Daniels' throwing ability, but it's what's circulating between his ears that has them even more impressed.
"He's further along than most freshmen I've ever been around, and that's exciting," USC quarterbacks coach Bryan Ellis said. "He wants somebody to tell him something at all times, and that's fun as a coach to understand that he's gonna always soak it up like a sponge."
Another fun subplot in this growing QB rivalry is the fact that they are already familiar with each other. Daniels got the better of Thompson-Robinson last September, with Mater Dei's 35-21 victory snapping Bishop Gorman's 55-game win streak. Thompson-Robinson, who has kept tabs on Daniels ever since, threw two costly interceptions in the loss and it's still eating him up.
"I definitely want my rematch," he said. "I honestly can't wait. I was so pissed that we lost because we could have won that game. When I get my opportunity, he better believe I'm gonna take it. I can't wait."
And maybe that shot at redemption will in fact come quickly. Neither the Bruins nor the Trojans got much accomplished at quarterback this spring.
Sears and Fink were uncomfortable turnover machines through the first half of spring, and neither improved enough to generate much confidence in the position exiting spring.
Kelly focused mostly on installation this spring, but Modster and Lynch fought inconsistency the whole time, resulting in shaky spring game performances for both.
Speight threw for more than 3,000 yards in three seasons at Michigan, but he's returning from a back injury.
Arizona's Khalil Tate, who had 1,411 rushing yards in 11 games last season, could see his Heisman hopes elevated with the arrival of Sumlin, but his throwing ability is still a question after he threw nine touchdowns to seven interceptions in Pac-12 play. Manny Wilkins has a new head coach and offense at Arizona State, and Stanford spent the spring with a walk-on at quarterback because K.J. Costello and Davis Mills were hurt.
The ambiguity under center in the Pac-12 helps the cause for the freshmen, but these coaches also understand how crucial early development is for these young quarterbacks. The playing field might seem more level, but coaches want to make absolutely sure before setting these QBs free.
"You have to be smart enough as a coaching staff to say, 'OK, this is what we can handle at this moment, right now, and let's lean on our strengths,'" Helton said. "It's unrealistic to come out here and say, 'Hey, he's going to be Sam Darnold or Matt Barkley or Cody Kessler day one.'"