Update: KJ Costello has officially been ruled out for the USC game.

A showdown between KJ Costello vs. JT Daniels, two top-ranked quarterbacks, was supposed to draw national attention. Suddenly, after week one, the narrative has changed into the battle of the backups, following injuries to both starters.

Davis Mills will likely start under center for the Cardinal Saturday night and undoubtedly gives Stanford the edge at quarterback. David Shaw has evident confidence in the third-year man, drawing him up 14 of Stanford’s 34 total passing attempts in the opening win. The only mistakes Mills made were a couple of handoff miscues and a few overthrows. Those blunders should be corrected come game day.

Meanwhile, the Trojan quarterback, Kedon Slovis, is a true freshman who didn’t expect to see much action this year. Slovis looked solid in the win versus Fresno State, but the Trojan offense struggled more with Slovis behind center, reaching the end zone only once.

With two backup quarterbacks playing, this game becomes less predictable, leaving the victory in the hands of the best defense.

The Cardinal defense, led by cornerback Paulson Adebo, looked surprisingly good against Northwestern. They forced two interceptions, and the Wildcat quarterbacks struggled. USC, which hired a new offensive coordinator, planned to use the air raid offense this year. In USC’s opener, JT Daniels threw the ball 34 times in the first half versus Fresno State before exiting with a knee injury. Now, the Trojans have an identity crisis. Their backup only threw the ball eight times in the second half, and the Trojans resorted to their run game, which could test Stanford’s defensive front more than the Wildcats in week one.

Vavae Malepeai ran for 134 yards against Fresno State, and former freshman phenom Stephen Carr is back after battling injuries last season. Stanford will need to win the trenches, something they proved they are capable of in week one.

Meanwhile, the Trojan defense inexperience showed versus Fresno State. The Bulldogs scored 23 points and collected 462 total yards with a new quarterback under center. Notably, quarterback Jorge Reyna shined, throwing for 256 yards and running for 88. In other words, Davis Mills will have the opportunity to show off his arms and legs.

The battle of backups is hard to predict, mainly because we have only seen both quarterbacks in limited action. At the end of the day though, Mills is more experienced and more talented than his USC counterpart. No, he did not lead the Cardinal offense into the end zone, but the offense showed flashes of its potential. I trust that with a week practicing with the first team Mills will be more comfortable leading the Cardinal to a 24-17 victory.

Tune in Saturday at 7:30 PT on ESPN.