The Trojans will face off against No. 23 Stanford this Saturday for the 100th time in history, but this time the game will be highlighted by unfamiliar signal-callers at the quarterback position.

Injuries to sophomore USC quarterback JT Daniels and senior Stanford quarterback K.J. Costello have forced the two Pac-12 programs to turn to their backup quarterback options.

True freshman Kedon Slovis, who came in for the Trojans after Daniels suffered a torn meniscus and ACL injury in the second quarter of last week’s 31-23 win over Fresno State, will look to lead USC’s offense past Stanford’s highly touted defense, which held USC to just three points in their 2018 matchup.

“You hate to see someone get hurt,” offensive coordinator Graham Harrell told reporters after practice on Tuesday. “But the season goes on. You got to continue to play, and we’ve had a ton of confidence in Kedon since he’s been here.”

Meanwhile for the Cardinal, junior Davis Mills will replace Costello, who is out with a head injury that he sustained during Stanford’s 17-7 win against the Northwestern Wildcats.

Slovis, a former three-star recruit from Scottsdale, Ariz., received considerable playing time in his collegiate debut, though he did not necessarily rack up his stat sheet; Slovis had just eight pass attempts and six completions for 57 yards with one interception. One of those passes, a 41-yard dot to redshirt junior wide receiver Tyler Vaughns, helped set up a touchdown by redshirt junior running back Vavae Malepeai that cushioned the Trojans’ lead down the stretch.

With USC leading the Bulldogs at halftime and an inexperienced quarterback, Harrell and head coach Clay Helton looked to secure the ball on the ground. Helton called Daniels’ injury “gut-wrenching,” during the postgame press conference, but added that he’s confident in Slovis’ abilities.

“We've always trusted our evaluations on guys,” Helton later said in a media teleconference on Sunday. “We believe in our evaluation. In Kedon's case, we saw a tremendous arm talent and we also saw an incredibly football-knowledgeable kid.”

Costello, like Daniels, went down right before halftime against the Wildcats, forcing the Cardinal to bring in Mills. The former five-star recruit from Duluth, Ga., made more passing attempts than Slovis last week, but with a far lower completion percentage; Mills went seven-for-14 against Northwestern with two fumbles.

Head coach David Shaw told the media that regardless of the obvious mistakes, Mills “did a good job of making decisions in the pocket.” Mills’ two extra years of experience over Slovis could serve to benefit Stanford as they visit USC at the Los Angeles Memorial Coliseum.

However, the new faces at quarterback are far from the only storylines set to continue on Saturday.

Stanford’s star offensive lineman, junior left tackle Walker Little, dislocated his knee during the Northwestern game. This opens up a void that the Trojans could take advantage of with their pass-rush game, led by redshirt senior Christian Rector and freshman Drake Jackson. Getting to Mills through that weak spot could dramatically change the course of the game for USC.

“[Jackson] is a super dynamic player and he picks up stuff really quickly,” Rector said on the Trojans Live podcast on Tuesday. “For me, I took it as my job to bring him along as quickly as possible and just make the transition to college football smooth for him.”

Both teams’ rushing games will also be looked at closely, with the two programs heavily using their running backs during their respective wins last week. Malepeai rushed for a total of 134 yards on 23 carries and posted a touchdown against Fresno State, while junior running back Stephen Carr had 12 touches on 99 total yards and 2 touchdowns.

Stanford’s senior running back Cameron Scarlett racked up 124 total yards last week. A strong run defense, as a result, will be crucial in a potential win for either team. USC allowed Fresno State to run for 206 yards while Stanford held Northwestern to just 93 rushing yards. Look for both squads to use their legs frequently.

Lastly, a familial battle will take place at the receiver position, with USC sophomore Amon-Ra St. Brown setting up to play against his brother, junior Osiris St. Brown.

Both receivers arrived at their respective programs with high expectations. Osiris arrived at Stanford as a four-star recruit in 2017, while Amon-Ra enrolled at USC in 2018 as the second best receiver in the nation. While Osiris was quiet against Northwestern, Amon-Ra had five receptions for 38 yards against Fresno State. Expect Slovis to throw to St. Brown frequently, along with Vaughns and senior Michael Pittman Jr.

Slovis and the Trojans will look to get back at Stanford for last year’s loss on Saturday in a nationally televised battle in Los Angeles at 7:30 p.m.

Follow @AnnMediaSports on Twitter and Intsagram for live coverage of Stanford vs USC.

Sept. 7, 7:06 p.m. - A previous version of this article stated that USC and Stanford were facing off for the 99th time in history. It has been corrected to the 100th game. USC had one game vacated in 2005. Annenberg Media apologizes for this error.