Marvin Lewis
When Sean McDermott was looking for his defensive coordinator, he elected to go with an experienced coach with prior head coaching experience. If he wanted to go that route again, a coach like Marvin Lewis wouldn’t be a bad option.
Lewis spent 16 years as the Cincinnati Bengals head coach but has plenty of experience on the defensive side of the ball. In fact he was the defensive coordinator for the Baltimore Ravens from 1996 to 2001 during a time the Ravens ranked nearly the top in almost every defensive category.
He is currently co-defensive coordinator for Arizona State University but had interviewed with the New York Jets, Houston Texans and Detroit Lions this offseason. If he wants to return to the NFL, there may not be a better landing spot than the defensive coordinator for the Bills.