The St. Louis Cardinals chose Junior in the first round (fourth pick overall) of the 1981 NFL Draft, and he played for Cardinals from 1981 to 1988. He was a two-time Pro Bowl selection for the Cardinals in 1984 and 1985. He subsequently played for the Miami Dolphins, Tampa Bay Buccaneers and Seattle Seahawks.
Since leaving the NFL, Junior has been the executive director of youth programs in Miami under the NBA's Alonzo Mourning. He also spent time back in the NFL as a coach and in the front office. He was the Seattle Seahawks linebacker coach in 1994 and then was the director of player development programs for the Miami Dolphins from 1996-1998. He has been a minority intern coach for the Minnesota Vikings (2003) and Jacksonville Jaguars (2005) and coached in NFL Europe for the Rhein Fire in Düsseldorf, Germany. On the college setting, he coached the linebackers at the 2005 and 2006 East-West Shrine Game.