Humm was selected by the Oakland Raiders in the fifth round of the 1975 NFL Draft with the 128th overall pick, partly because he was ambidextrous. The next year, he was a part of the Super Bowl XI championship team. He was the backup to Ken Stabler for five seasons and was also an effective holder for field goals or extra points. Humm had an unusual habit of going on to the field with no shoulder pads, which sometimes tipped the opposing team that a fake field goal was unlikely. In 1981, he signed as a free agent with the Baltimore Colts. That year, the game between the Colts and the Dallas Cowboys was the only start in his NFL career when injuries sidelined Bert Jones and Greg Landry. He completed seven of 24 passes for 90 yards and two interceptions, in a 13–37 loss, the thirteenth consecutive for the Colts. Notably, the opposing quarterback for the Cowboys, Glenn Carano, was also making his first and only NFL start in place of Danny White This is the only time in league history two "one and done" quarterbacks have ever faced off Carano and Humm were the subjects of an NFL Films piece entitled My One and Only, recounting the 1981 game. The two quarterbacks had been friends since high school, and remained friends until Humm's death. In 1983, he was signed as a free agent by the Los Angeles Raiders. That season, he was a part of the Super Bowl XVIII championship team, serving as the third-string quarterback behind Jim Plunkett and Marc Wilson. Humm was the only Raiders player to be a member of both the Raiders' 1976 Super Bowl XI and 1983 Super Bowl XVIII championship teams, without also being a member of the 1980 Super Bowl XV championship team. Humm's last NFL action came in a Week 10 contest in 1984 against the Chicago Bears, a game which has been considered one of the most violent games in NFL history.
Personal life
After his playing career, Humm served as an analyst for Mutual Broadcasting System, the Las Vegas Posse, and the Oakland Raiders. In 1988, Humm was diagnosed with multiple sclerosis at age 36 and lost the use of his legs in 1997. He had set up a broadcasting studio in his home and worked as a color commentator for the Oakland Raiders. Humm died due to complications from multiple sclerosis on March 27, 2018.