Kerns was selected in the seventh round (180th overall) of the 1976 NFL Draft by the Patriots, and he played for the team for seven seasons. He played for Tampa Bay for two seasons, then one each for the Giants and Redskins before returning to Tampa Bay for his final three seasons. He was a member of the 1982 Buccaneers team that won the NFC Championship and advanced to Super Bowl XVII, where they lost to the Washington Redskins.
After his playing career ended, Kerns became an actor and has appeared in a number of movies and television shows, including:
Movies:
- The Longest Yard (1974)
- The Right Stuff (1983)
- Wildcats (1986)
- The Color Purple (1985)
- Predator (1987)
- Ernest Goes to Jail (1990)
- The Waterboy (1998)
- The Animal (2001)
Television shows:
- The A-Team (1983–1987)
- Riptide (1984–1986)
- Miami Vice (1984–1989)
- Hunter (1984–1991)
- The Equalizer (1985–1989)
- Magnum, P.I. (1980–1988)
- The Commish (1991–1996)
- Walker, Texas Ranger (1993–2001)