Cook was dressed and warming up before Saturday’s kickoff, but did not take the field for the Spartans’ first offensive drive of the game. Cook had started 36 consecutive games at quarterback for Michigan State.
Cook, a senior, sustained a shoulder injury in last week’s 24-7 victory over Maryland. Cook appeared in pain after he was tackled during the first quarter and left the game briefly before returning to play the remainder of the first half. He was sidelined in the second half and O’Connor came in to replace him.
Cook was 6 of 20 for 77 yards with an interception in the first half. O’Connor finished the game going 6 for 11, throwing for 44 yards and a touchdown.
On Tuesday, Cook said his shoulder was fine and that he would be ready to go.
No. 9 Michigan State (9–1) is playing No. 3 Ohio State on the road.