He is best known in the United States as the head coach of the New England Patriots of the National Football League (NFL) during the 1990 season, which ended with a 1–15 record.
Rust returned to work for Levy in 1973 as defensive coordinator for the Montreal Alouettes of the Canadian Football League.
He served as linebackers coach for two seasons before leaving to take the defensive coordinator position with Levy and the Kansas City Chiefs.
Rust and the Patriots went to Super Bowl XX (under head coach Raymond Berry) in 1985, but he left the team after the 1987 season.
Rust was named the head coach of the Montreal Alouettes of the Canadian Football League in 2000, and was fired during the 2001 season after a six-game losing streak.
He returned to the CFL in 2005, taking the coordinator position with the Winnipeg Blue Bombers; he left abruptly halfway through the season.