 In 1981, he got his first NFL coach job when Marv Levy hired him as linebackers coach for the Kansas City Chiefs.Considered an innovator in the 3–4 defense, Cottrell was an assistant coach for the Buffalo Bills from 1995 to 2000, the last three seasons as defensive coordinator.From 1998 through 2000, the Bills finished no worse than sixth in the league in total defense.