Williams, who joined the Tennessee Titans in 2018 as a longtime defensive line coach, will step in for head coach Mike Vrabel during Saturday's pre-season game against Chicago.
Sunday's game will be delayed until Monday or Tuesday. This comes after four players and five staff members reportedly contracted COVID-19.
The Chiefs beat the Tennessee Titans 35-24 in the AFC Championship on Sunday. The 49ers followed with an NFC victory over the Green Bay Packers, 37-20. The Chiefs and 49ers will meet in Miami Feb. 2.