When Jim Colletto was hired to replace Fred Akers after the 1990 season, he retained Brock as a defensive coach from 1991–1994.
In the 2008 season, Danny Hope was hired to return to Purdue to become head coach in 2009 upon Joe Tiller's retirement.
Spack coached with Hope during the 2008 season under Tiller and had indicated his intention to stay on Hope's staff, but ultimately, when offered a head coaching position at Illinois State, Spack decided to leave his alma mater starting with the 2009 season.
During the 2021 season, Spack became the winningest coach in Illinois State history; passing Edwin Struck's mark of 86 wins.
During the 2023 season, Spack reached the 100-win plateau with the Redbirds win over Missouri State on November 4th.