The Cowboys continued to develop their roster in the offseason and Shannon was cut at the end of the preseason in 1990. He returned to the Cowboys and appeared in a few games in September but was released on October 1, concluding his professional playing career. During his time in the league, Jimmy Johnson credited Shannon with teaching his "bigger, faster linebackers how to play the position." During his NFL career, Shannon played in 17 regular season games during the 1989 and 1990 seasons, starting four of them.