Miller spent one season at UofL, serving as the Cardinals linebacker coach.
"The timing of this is opportunity is very unfortunate," said Miller. "But it's an opportunity for me to be closer to my 85-year old father and my brother. I truly appreciate the opportunity Steve gave me at Louisville, and am grateful of the treatment that Tom Jurich and Steve also gave me while I was here. I don't expect many people to understand my decision, but this is something I had to do for my family."
It's been a turbulent off-season for the Louisville coaching staff. Former defensive coordinator Ron English left to become the head coach at Eastern Michigan, taking defensive back coach Eric Lewis with him. Special teams coach Mark Nelson left this week to accept a position in the Canadian Football League. It's also expected that Jeff Brohm won't remain as Louisville's offensive coordinator, the position he was promoted to before the 2008 season.
Kragthorpe said he would name a new defensive coordinator next week. Louisville announced the hiring of former Utah State head coach Brent Guy and former Tennessee assistant Larry Slade as defensive assistants this week. The Cardinals also hired former Southern Miss offensive coordinator Jay Johnson as an offensive assistant.
"Bill has an opportunity to move back to his home state to be closer to his father and other family members," said Kragthorpe. "I wish him and his family all the best."