Marinelli's coaching career began in 1973 as an assistant at Rosemead High School in suburban Los Angeles from 1973 to 1975.
He earned his first collegiate job in 1976, serving as an assistant to head coach Bruce Snyder at Utah State University until 1982.
[1] Marinelli worked to develop linemen, such as Warren Sapp and Simeon Rice, into Hall of Fame caliber players.
Marinelli was the third head coach hired (within five seasons) by Lions CEO Matt Millen, preceded by Marty Mornhinweg and Steve Mariucci.
The Marinelli era began poorly, as the Lions lost the first five games of the 2006 season before edging the Buffalo Bills 20–17.
The Lions lost seven games in a row between Weeks 10 and 16, before ending the year on a high note by defeating the Dallas Cowboys 39–31.
[2] The combined record during his three seasons with the Lions was 10–38, one of the worst in NFL history for a head coach with at least three years' experience.
On February 5, 2020, Marinelli was named the defensive line coach for the newly relocated Las Vegas Raiders.