Stanford rules out QB Costello vs. USC

Stanford quarterback K.J. Costello will not play on Saturday against USC, coach David Shaw announced Thursday.

The senior quarterback exited just before halftime of last week's 17-7 win against Northwestern after receiving a hit to the head. Redshirt sophomore Davis Mills will start in his place.

Costello was going into a sliding motion against Northwestern when he absorbed a forearm to the head, but the play did not draw a targeting penalty.

"I believe the officials on the field and replay officials missed the call," Shaw said this week. "I thought it was an ejectable offense. I've communicated with a lot of different people in a lot of different places. It was unfortunate it was missed."

Mills, ESPN's No. 2-ranked ranked pocket passer in the Class of 2017, was 7-for-14 for 81 yards in relief of Costello, a second-team All-Pac-12 selection last year.

USC will start true freshman Kedon Slovis at quarterback after starter JT Daniels was lost for the season with a torn ACL and meniscus during Saturday's win against Fresno State.

Shaw also announced earlier this week that All-America-caliber left tackle Walker Little will be out until at least midseason due to a lower body injury suffered against Northwestern.