[1] Alzado played for the Denver Broncos, the Cleveland Browns, and finally the Los Angeles Raiders with whom he won a championship in Super Bowl XVIII.
[1][7][9] Though playing in relative obscurity in the NAIA, Alzado nonetheless gained notice by the NFL when Denver Broncos' coach and scout Stan Jones having been taken off the road by automobile trouble, decided to pass the time at nearby Montana Tech, one of Yankton's opponents.
[7][10] Montana Tech's coaches were showing him films of their star running back Don Heater, but Jones was impressed with the unknown defensive lineman Alzado squaring off against Montana Tech's offense and passed back a favorable report to his team.
When the Broncos' starting right defensive end Rich "Tombstone" Jackson was injured in 1971, Alzado took over the job and went on to make various All-rookie teams for his contributions of 60 tackles and 8 sacks.
In 1973, Alzado posted excellent numbers as the Broncos had a winning record for the first time in team history with a 7–5–2 mark.
In 1974, Alzado gained more notice as one publication named him All-AFC; with his 13 sacks and 80 tackles (eight for a loss), he was recognized as one of the NFL's top defensive ends, along with Elvin Bethea, Jack Youngblood, L. C. Greenwood, Claude Humphrey, and Carl Eller.
The Broncos were 9–5 but SPORT magazine reported that 12 players, including Alzado, did not think the team could reach the playoffs with coach John Ralston.
The 1977 season was the most successful in franchise history to that point; the Broncos had one of the NFL's best defenses, went 12–2 and then beat the Pittsburgh Steelers and Oakland Raiders - the team for which he later starred - in the playoffs to reach Super Bowl XII.
After demonstrating dominant play throughout the strike-shortened 9-game season of 1982, he was voted the NFL Comeback Player of the Year.
In 196 career games, he racked up 112 sacks, 24 forced fumbles, and nearly 1,000 tackles, while earning Pro Bowl honors in 1977 and 1978.
After his retirement from playing, Alzado worked as a part-time color analyst for NBC's NFL coverage in 1988–89.
In 2018, the Professional Football Researchers Association named Alzado to the PFRA Hall of Very Good Class of 2018.
"[8] Defensive end Greg Townsend, a teammate on the Raiders said that the savagery for which Alzado became noted represented part of a "split personality."
[14][15] He was involved in "countless youth organizations", receiving the Byron "Whizzer" White award for community service in 1977.
Alzado pursued an acting career in both movies and television, appearing mostly in youth-oriented comedy and adventure roles.
His most notable film roles include the bully construction worker in Ernest Goes to Camp and the unstoppable killer in Destroyer.
Alzado appeared in the series premiere of the short-lived 1991 sitcom Good Sports with Ryan O'Neal and Farrah Fawcett, and in episodes of It's Garry Shandling's Show and MacGyver.
In the last year of his life, as he battled against the brain tumor which eventually caused his death, Alzado asserted that his steroid abuse directly led to his fatal illness.