Eddy's coaching career began as a high school coach in Odessa, Texas. He was later named head coach at
Roswell High School. In 1968, he joined the coaching staff at his alma mater,
New Mexico State University, where he was an assistant head coach and defensive coordinator. In 1972, he joined
Tommy Hudspeth's
UTEP Miners coaching staff as the defensive coordinator. Eddy's next coaching job was as the
defensive coordinator of
Saskatchewan Roughriders, which he held until he was promoted to
head coach in 1977. In Eddy's first season, the Roughriders went 8–8 and missed the playoffs only one season removed from playing the
Ottawa Rough Riders in the
64th Grey Cup. Eddy was fired during the 1978 season after the Riders lost their first five games. In 1979, Eddy joined the
Hamilton Tiger-Cats coaching staff, where he was reunited with his former boss in Saskatchewan,
John Payne. His next coaching job was with the
Montreal Alouettes, first as the defensive backfield coach, then as the Als interim head coach. In 1982, he moved to the front office as Director of Operations and Player Personnel of the
Toronto Argonauts. Along with head coach
Bob O'Billovich, he helped rebuilt an Argonauts team that had gone 2–14 the prior season into a team that won the
East Division championships in both of Eddy's seasons there and won the
71st Grey Cup in 1983. Eddy was the defensive coordinator of the
Houston Gamblers for both of the team's seasons in the
United States Football League (USFL). He contributed to the team reaching the playoffs both years and winning a Division Title in 1984. In 1987,
Jack Pardee hired Eddy to become defensive coordinator of the
Houston Cougars football team. He spent three seasons there, helping the school post a 22-11-1 record, while leading the
Southwest Conference in defense in 1988 and 1989. In his final season, the defense finished sixth in the nation in scoring defense. Eddy followed Pardee to the
Houston Oilers, where he remained the coach's defensive coordinator in 1990. His defense led the American Football Conference, while finishing third in the league in total defense, third in the NFL in pass defense and tied for fifth in sacks. The Oilers earned three playoff berths, including the club's first AFC Central Division crown in 1991. He was fired following the Oilers
1992 playoff loss to the
Buffalo Bills in an infamous game which would become known as
The Comeback, when the team lost 38–41, after being in front 35–3, early in the third quarter. He joined the
Dallas Cowboys coaching staff in 1993 as a defensive assistant and later as the team's linebackers coach. While in Dallas, he helped win two
Super Bowls. In 1996, Eddy became the
Detroit Lions defensive coordinator. He would hold that job for only one season. He decided to retire in 1997. In 2000, he was one of the candidates for the vacant Cowboys head coaching position, but lost the job to
Dave Campo. ==Personal life==