According to STATS Inc., only six teams in the four major sports have failed to post consecutive winning seasons. Here they are by sport, with the years they entered their respective leagues:
NFL – Atlanta Falcons (1966), Carolina Panthers (1995), Houston Texans (2002)
MLB – None
NBA – Charlotte Bobcats (2004-05)
NHL – Atlanta Thrashers (1999-00), Columbus Blue Jackets (2000-01)