Assistant head coach/defensive line coach Larry Johnson will serve as interim head coach on Saturday while Day is in isolation.
Ohio State has confirmed "an increased number of positive tests this week for the coronavirus," but it continues to prepare for its noon game in Champaign, Illinois.
The Buckeyes completed another round of daily testing on Friday morning, and everyone associated with the team -- including coaches and support staff -- will also take PCR tests on Friday afternoon "out of an abundance of caution to ensure that everyone on the trip is confirmed negative for the coronavirus," according to a news release.
Because of the additional PCR testing, the team will fly to Champaign on Saturday morning instead of Friday afternoon.
A school spokesman told ESPN that Day informed the team of his positive test around 3 p.m. ET Friday; the Buckeyes weren't planning on leaving until 9 p.m. Friday anyway because they can't eat together or be in meeting rooms together once in Illinois because of social distancing measures.
Ohio State typically likes to arrive at its games about two hours before kickoff, so a Saturday morning departure isn't expected to be a major setback. Because Illinois is on Central time and Ohio State is on Eastern, they also have a little bit more flexibility. Anyone in the program who is taking follow-up PCR tests Friday afternoon has already tested negative.
The department has kept the University of Illinois and the Big Ten Conference aware of the developments.
"I have spoken with Coach Day, and he is doing well physically," athletic director Gene Smith said. "I feel terrible for Coach and for the members of the program who have been diagnosed with a positive test.
"Coach Day and this team have been true leaders in handling things so well throughout this pandemic. Our team wants to play this game, and we're going to do everything we can to help make this happen. All of the decisions on the welfare of our student-athletes and staff members will continue to be guided by our medical staff."
According to the school, Ohio State has "consistently recorded nearly 0% positivity since Aug. 11," and while there has been an increase in positive tests, it still doesn't reach the threshold for Ohio State to have to cancel the game this week, according to Big Ten protocols.
Ohio State's Nov. 14 game at Maryland was canceled because of COVID-19 within the Terps' program.