One of the fiercest Chicago Bears defensive players in the franchise’s history announced Friday he has ALS, also known as Lou Gehrig’s disease.

Steve McMichael, an NFL defensive tackle who was an All-Pro for the Super Bowl-winning 1985 Bears, was being interviewed by Jarrett Payton, a broadcaster for WGN in Chicago who is also the son of another Bears legend, the late Walter Payton.

“I’m not going to be in the public anymore,” McMichael said, as reported by Pro Football Talk. “You’re not gonna see me out doing appearances. I can’t even sign my name anymore.”

McMichael, 63, had a College Football Hall of Fame career at Texas and was a third-round pick of the Patriots in 1980. New England cut him after one season, and he signed with Chicago, where he played for 13 seasons, winning a Super Bowl ring and being named first-team All-Pro in 1985 and 1987.

He played his final season with the Packers in 1994.

He had a post-football career as a professional wrestler and commentator with Atlanta-based World Championship Wrestling.

According to the ALS Association, amyotrophic lateral sclerosis is a progressive degenerative disease that affects nerve cells in the brain and the spinal cord.

Other former NFL players who have been diagnosed with ALS include Steve Gleason, Dwight Clark, O.J. Brigance, Kevin Turner and former Atlanta Falcons standout Tim Green. Some neurologists believe there is a link between head trauma suffered on the football field and the development of ALS, although the ALS Association says more long-term studies are needed for a full understanding of the connection between football and ALS.