Born in Akron, Ohio, Simon grew up in El Paso, Texas. He attended Burges High School where he was a three-sport standout in football, track and wrestling. He earned four letters as a linebacker for the Eastern New Mexico University Greyhounds and was later inducted into the ENMU Hall of Honors. Immediately following his playing career, Simon began his coaching career as a graduate assistant at his alma mater. After one year as an assistant at Borger High School, Simon coached the tight end and linebacker positions at the University of Texas at El Paso under head coach Bill Michael.
In 1982 he became running backs and placekickers coach at the University of Washington. The Huskies went to nine bowl games over a span of ten seasons. In 1991 the Huskies tied the University of Miami for the national championship. In 1997 Simon was inducted into the University of Washington’s Hall of Fame. Simon left Washington in 1992 for the offensive coordinator position at New Mexico under head coach Dennis Franchione. The Lobos averaged 413 yards and 30.5 points per game during that span. They ranked 13th in the country in 1992 and improved to 8th the following year.
Simon succeeded Dennis Parker as head coach at North Texas in 1994, becoming only the 10th African American to lead a Division I-A football squad. In his first season, Simon guided North Texas to the Southland Conference Championship. He was named Southland Conference Coach of the Year, Black Coaches Association National Football Coach of the Year and AFCA Region 4 Coach of the Year. However, the Mean Green football program decline the next years, causing Simon to be fired in 1997.
After coaching at the Denver Broncos training camp in 1998, Simon began his pro coaching career with the Baltimore Ravens. Under his guidance, Baltimore rushed for an average of 1,985 yards per season and defeated the New York Giants in Super Bowl XXXV following the 2000 NFL season. In 2004, the Ravens’ ground attack produced 2,063 total yards and ranked 9th in the NFL. It was Jamal Lewis’ fourth 1,000-yard rushing season under Simon. Baltimore rushed for at least 2,000 yards in three different seasons under Simon, including a team-record 2,674 yards in 2003 when Jamal Lewis was named NFL Offensive Player of the Year, Associated Press All-Pro and selected to the AFC Pro Bowl squad.