Butz was drafted in the first round (fifth overall) of the 1973 NFL Draft by the St. Louis Cardinals, where he would play for two seasons. Redskins coach George Allen gave the Cardinals two first-round draft picks and a second-rounder for the right to Butz. Butz then played for the Washington Redskins for 14 years, where he had three Super Bowl appearances. He ranks third in franchise history in sacks (59.5). He was a one time Pro Bowler in 1983 in a season in which he got eleven sacks, a career best. He only missed four games in his entire 16-year career. Butz was among the largest players in the NFL when he played standing 6'8" and routinely weighing around 300 pounds. When he retired, he was the oldest starting player in the NFL.
Butz was selected to the NFL 1980s All-Decade Team and was named one of the 70 Greatest Redskins.
In 1975 Butz was granted free agency due to a mistake in his contract that he signed as a rookie in 1973. George Allen quickly signed him, but the NFL ruled that the Redskins had to pay the Cardinals 2 first round picks (1977 & 1978) and a second round pick (1979). Washington Post 1975.