LOS ANGELES >> Sam Darnold and Josh Rosen were born four months apart in 1997, and they grew up on opposite sides of Los Angeles’ sprawling metroplex. As two of the nation’s top quarterback prospects, they chose opposing sides in the crosstown collegiate rivalry.

After a redshirt season and an injury kept them apart for two years, they’ll finally meet on the field for the first time Saturday.

Rosen leads UCLA (5-5, 3-4 Pac-12) into the Coliseum to face Darnold and No. 12 Southern California (9-2, 7-1) in what might be LA’s only chance to see both of its big-time NFL prospects between the same hash marks.

“I think there’s something cool there,” Darnold said. “It’s awesome. It’s a really cool story line to be able to be linked with Josh, to be in the same class as him coming out of high school, all that stuff. But I think when it comes down to it, it’s just two quarterbacks competing. We just happen to be pretty good players.”

Although the Trojans are big favorites with the Pac-12 South title already clinched, this passing matchup adds another exciting ingredient to the rivalry game for the Victory Bell. The moment isn’t lost on Darnold, who realizes he’ll probably be linked for life with Rosen as their football careers progress on similar timelines.

“Josh is a great guy, so if that happens to be the case, that would be sweet,” Darnold said. “A great player like Josh, a great guy like Josh, I wouldn’t have any problem with that.”

Darnold and Rosen have become friends under the spotlight, and they occasionally talk or text. Unlike many fans, they realize this rivalry game is not a referendum on which passer is more talented.

They’re both surefire NFL prospects, and they could be the first two quarterbacks selected next spring if they declare their eligibility for the next draft. While scouts and executives have been debating their relative merits for months, they’ve both proven their potential during three years of college ball at campuses 11 miles apart.

“I think he’s a really special player,” Rosen said with a grin. “He’s definitely more athletic than I am.”

USC coach Clay Helton has been watching their development since his first year on the Trojans’ staff eight seasons ago: He first saw Rosen as an eighth-grader in Pop Warner ball, where he played on the same team as Helton’s son at one point.

“Being a quarterback coach by trade, it’s been very, very impressive to watch him grow up,” Helton said.

After Rosen’s high school career at urban St. John Bosco and Darnold’s parallel play at coastal San Clemente High School in Orange County, they both stayed close to home.

Rosen, widely considered the best quarterback in the national class, enrolled early and stepped right into the Bruins’ starting lineup as a freshman, eventually passing for 3,670 yards and 23 touchdowns.

Darnold, who grew up a USC fan, didn’t hesitate to commit to the Trojans despite their annual logjam at quarterback. He watched the 2015 season from the sideline as a redshirt while three-year starter Cody Kessler finished his career and Max Browne backed him up.

The quarterbacks’ fortunes changed dramatically last season.

Rosen got off to a strong start as a sophomore, but injured his shoulder midway through the season and eventually needed surgery. He missed half the year, and the Bruins crashed to 4-8 without him.

Darnold spent three games as a backup before Helton promoted him past Browne with the Trojans at 1-2. Darnold lost his starting debut — and then never lost again, winning nine straight games capped by a Rose Bowl-record 473 yards of total offense and five TD passes in an epic win over Penn State.

Darnold and Rosen entered their third collegiate seasons with a world of hype surrounding them. NFL scouts have crowded the stands at each of their games, even while their play and their teams’ fortunes occasionally failed to live up to the all-but-impossible expectations.

While the Trojans have outplayed the Bruins overall, their quarterbacks’ raw numbers are remarkably similar. Darnold has passed for 3,198 yards with 24 touchdowns and 11 interceptions, while Rosen has 3,094 yards passing with 21 touchdowns and nine interceptions despite missing one game due to a concussion.

They probably won’t meet again until a future NFL Sunday, so Darnold and Rosen intend to enjoy every aspect of what should be a memorable moment.

“I think it’s awfully exciting to see these two really fine young quarterbacks that are good leaders and great competitors taking the field together on Saturday night,” UCLA coach Jim Mora said. “It’ll be a fun game for people to watch.”