Stanford quarterback K.J. Costello left Saturday's game against Northwestern after taking a vicious forearm to the head from Wildcats defensive end Earnest Brown.
The play happened at the end of the second quarter, and Costello remained sidelined to start the second half.
Brown was penalized for a late hit, but he avoided a targeting call and stayed in the contest. Davis Mills took over for Costello to start the second half.
